Unit 5 Into the unknown
课后培优——微积累战高考，训练提分点
简化与合并(1)
概要写作要求用60词左右概括一篇350词左右的文章，因此需要对冗杂的信息进行简化和合并，以达到概括的目的。简化和合并信息可以采用下列几种技巧：
1．删除细节：剔除细节信息，只保留主干内容。
In addition, if the school buys automatic hand dryers, we can save money.There is a terrible waste of paper towels in the restrooms.
→Additionally, it can help the school save money.
2．简化描述：把长段的描述变成短小、简单的句子。如果材料中描述某人或某事用了好几个句子，那么你只要把它们变成一两句即可。
There were 30 cows on the farm that his grandmother had to milk every day.It was hard work for his grandmother.
→His grandmother worked hard milking 30 cows daily.
3．避免重复：在原文中，为了强调某个主题，可能会重复，应该删除或者合并这些重复信息。
They were waiting for the meeting to begin.They talked with each other.They talked about the women's football team.The team had won victories in Guangzhou.
→While waiting for the meeting to begin, they talked about the victories won by the women's football team in Guangzhou.
4．压缩长句：有些句子比较冗长，可以进行压缩和简化，使之简洁。
His courage in battle might without exaggeration be called lion like.
→He was very brave in battle.
小试牛刀
1．Motion sensing hand dryers are a practical alternative to paper towels(纸巾).I believe that our school would benefit from investing in automatic hand dryers in all the restrooms.
→Compared_with_paper_towels,_hand_dryers_have_more_advantages,_which_will_benefit_our_school_in_four_ways.
2．First of all, the automatic hand dryer is very sanitary(卫生的).No bacteria can get on them because there is nothing to touch.
→First,_they_are_clean_and_healthy_because_bacteria_can't_touch_kids.
3．When people dry their hands for at least 30 seconds, automatic dryers actually dry much better than paper towels.It is difficult to get every part of your hand dry using paper towels, but the air can if you take a few extra seconds.
→Besides,_it_can_dry_our_hands_more_effectively_if_we_take_longer_time.
4．As you see there are some good points, let's install automatic hand dryers as soon as possible.
→Therefore,_the_school_is_advised_to_fix_the_equipment_at_once.
5．You can obtain a large amount of information on the Internet nowadays.
→Abundant_information_is_available_on_the_Internet.
Ⅰ.阅读理解
语篇类型 夹叙夹议文
主题语境 人与自然——医学研究——已知的和未知的事物
(2020·江苏高考·D)I was in the middle of the Amazon (亚马逊) with my wife, who was there as a medical researcher.We flew on a small plane to a faraway village.We did not speak the local language，did not know the customs，and more often than not，did not entirely recognize the fooD．We could not have felt more foreign.
We were raised on books and computers，highways and cell phones，but now we were living in a village without running water or electricity.It was easy for us to go to sleep at the end of the day feeling a little misunderstooD．
Then one perfect Amazonian evening，with monkeys calling from beyond the village green，we played soccer.I am not good at soccer，but that evening it was wonderful.Everyone knew the rules.We all spoke the same language of passes and shots.We understood one another perfectly.As darkness came over the field and the match ended，the goal keeper，Juan，walked over to me and said in a matter of fact way，“In your home，do you have a moon too？” I was surpriseD．
After I explained to Juan that yes，we did have a moon and yes，it was very similar to his，I felt a sort of awe (敬畏) at the possibilities that existed in his worlD．In Juan's world，each village could have its own moon.In Juan's world，the unknown and undiscovered was vast and marvelous.Anything was possible.
In our society，we know that Earth has only one moon.We have looked at our planet from every angle and found all of the wildest things left to finD．I can，from my computer at home，pull up satellite images of Juan's village.There are no more continents and no more moons to search for，little left to discover.At least it seems that way.
Yet，as I thought about Juan's question，I was not sure how much more we could really rule out.I am，in part，an ant biologist，so my thoughts turned to what we know about insect life and I knew that much in the world of insects remains unknown.How much，though How ignorant(无知的) are we The question of what we know and do not know constantly bothered me.
I began collecting newspaper articles about new species，new monkey，new spider...，and on and on they appear.My drawer quickly filleD．I began a second drawer for more general discoveries: new cave system discovered with dozens of nameless species，four hundred species of bacteria found in the human stomach.The second drawer began to fill and as it did，I wondered whether there were bigger discoveries out there，not just species，but life that depends on things thought to be useless，life even without DNA．I started a third drawer for these big discoveries.It fills more slowly，but all the same，it fills.
In looking into the stories of biological discovery，I also began to find something else，a collection of scientists，usually brilliant，occasionally half mad，who made the discoveries.Those scientists very often see the same things that other scientists see，but they pay more attention to them，and they focus on them to the point of exhaustion (穷尽)，and at the risk of the ridicule of their peers.In looking for the stories of discovery，I found the stories of these people and how their lives changed our view of the worlD．
We are repeatedly willing to imagine we have found most of what is left to discover.We used to think that insects were the smallest organisms (生物)，and that nothing lived deeper than six hundred meters.Yet，when something new turns up，more often than not，we do not even know its name.
1．How did the author feel on his arrival in the Amazon
A．Out of place. B．Full of joy.
C．Sleepy. D．Regretful.
2．What made that Amazonian evening wonderful
A．He learned more about the local language.
B．They had a nice conversation with each other.
C．They understood each other while playing.
D．He won the soccer game with the goal keeper.
3．Why was the author surprised at Juan's question about the moon
A．The question was too straightforwarD．
B．Juan knew so little about the worlD．
C．The author didn't know how to answer.
D．The author didn't think Juan was sincere.
4．What was the author's initial purpose of collecting newspaper articles
A．To sort out what we have known.
B．To deepen his research into Amazonians.
C．To improve his reputation as a biologist.
D．To learn more about local cultures.
5．How did those brilliant scientists make great discoveries
A．They shifted their viewpoints frequently.
B．They followed other scientists closely.
C．They often criticized their fellow scientists.
D．They conducted in depth and close studies.
6．What could be the most suitable title for the passage
A．The Possible and the Impossible
B．The Known and the Unknown
C．The Civilized and the Uncivilized
D．The Ignorant and the Intelligent
Ⅱ.完形填空
语篇类型 记叙文
主题语境 人与自我——个人经历——异国求学的暖人故事
(2021·山东部分重点中学新起点摸底联考)This semester, I am studying abroad at Mahidol University in ThailanD．One day, I traveled to Kancheanaburi with two friends.After visiting our last destination, due to the __1__ of local transportation, we decided to take a long walk to the station to __2__ the last bus at 8 p．m. back.
However, when we arrived around 7：20 p．m., we were told by the staff there that we went to the wrong place.We did not even think about __3__ this could happen or where we actually were since the only __4__ then was how to get to the station on time.With no taxi on the road and no bus to the station, we were __5__ there.Seeing our anxiety, the staff said they could help us.The male staffer immediately stopped having his dinner and __6__ the motorcycle engine.However, that motorcycle, as the only transportation they __7__ at that time, could only take one passenger.It would take __8__ 15 minutes for a round trip.
Around 7：40 p．m., I was still there.Suddenly, a young man came to __9__ someone off with a motorcycle.The female staffer, who kept talking with me to alleviate(缓和)my worry, stopped him.After they spoke, he nodded, and she hurried me up to __10__ the motorcycle.I did not know who he was, but I could remember that he seemed as __11__ as I was, like the person who was about to miss the last bus back was him instead of me.He drove fast, which I normally would be afraid of, but I felt __12__ then.With my hands on his shoulder, I believed he would __13__ send me to the station safely.
Everything happened so quickly.It was not until the next day __14__ I knew we mistakenly went to their administrative (行政的)office at first.Although I have said“Thank you”to them several times, I still think it is not enough to express my appreciation.I know who they are now: They are the nameless people who are willing to selflessly help others, __15__love and warmth in society.
1．A．absence B．number
C．speed D．limitations
2．A．chase B．grasp
C．catch D．seize
3．A．how B．why
C．when D．what
4．A．dilemma B．approach
C．annoyance D．concern
5．A．stuck B．abandoned
C．blocked D．isolated
6．A．started B．set
C．fired D．launched
7．A．paid attention to B．had faith in
C．had a preference for D．had access to
8．A．no more than B．less than
C．more than D．more or less
9．A．drop B．take
C．leave D．send
10．A．get off B．get on
C．get in D．get into
11．A．frustrated B．annoyed
C．worried D．satisfied
12．A．in belief B．with respect
C．for sure D．at ease
13．A．desperately B．directly
C．definitely D．deliberately
14．A．when. B．that
C．which D．before
15．A．sparing B．spreading
C．transforming D．transmitting
Ⅲ.概要写作
阅读下面短文，根据其内容写一篇60词左右的内容概要。
In 1971，China's first subway line in Beijing was formally put into operation.By December 2017，there were 171 subway lines stretching over 5，083 km in 35 cities on the Chinese mainlanD．Currently，China has the longest urban railway network in the worlD．
The rapid development of China's urban railway system reflects the country's growing economic strength.The system has experienced the fastest growth over the past 15 years due to the investment of wealth accumulated from the reform and opening up in urban infrastructure construction.An urban railway system is expensive to build，with one kilometer of subway costing approximately 700 million yuan($110 million).A city without economic strength cannot develop such an expensive system.
The progress in urban railway construction technologies has also contributed to the fast expansion of the infrastructure.Subway construction involves building underground tunnels，laying rails，manufacturing trains and the operation and management of subways.It is a systematic project which not only covers traditional infrastructure building but also modern electronics and information technology.China's railway construction technologies are the best in the world，with Chinese subway trains now exported to developed countries including the United States.
The expansion of Chinese cities has made it necessary to develop urban railway systems.Since the start of the reform and opening up，a large number of people have migrated to cities and the number of private cars has increased dramatically，resulting in serious traffic congestion.Building subways has become an important way to solve this problem.
This year marks the 42nd anniversary of the launch of China's reform and opening up，and the rapid development of China's urban railway system exemplifies the achievements made by the policy.As China furthers its opening up，it will continue to maintain steady and rapid economic growth and railway systems will be available in more and more cities.
PAGE
9Unit 5 Into the unknown
课后培优——微积累战高考，训练提分点
简化与合并(1)
概要写作要求用60词左右概括一篇350词左右的文章，因此需要对冗杂的信息进行简化和合并，以达到概括的目的。简化和合并信息可以采用下列几种技巧：
1．删除细节：剔除细节信息，只保留主干内容。
In addition, if the school buys automatic hand dryers, we can save money.There is a terrible waste of paper towels in the restrooms.
→Additionally, it can help the school save money.
2．简化描述：把长段的描述变成短小、简单的句子。如果材料中描述某人或某事用了好几个句子，那么你只要把它们变成一两句即可。
There were 30 cows on the farm that his grandmother had to milk every day.It was hard work for his grandmother.
→His grandmother worked hard milking 30 cows daily.
3．避免重复：在原文中，为了强调某个主题，可能会重复，应该删除或者合并这些重复信息。
They were waiting for the meeting to begin.They talked with each other.They talked about the women's football team.The team had won victories in Guangzhou.
→While waiting for the meeting to begin, they talked about the victories won by the women's football team in Guangzhou.
4．压缩长句：有些句子比较冗长，可以进行压缩和简化，使之简洁。
His courage in battle might without exaggeration be called lion like.
→He was very brave in battle.
小试牛刀
1．Motion sensing hand dryers are a practical alternative to paper towels(纸巾).I believe that our school would benefit from investing in automatic hand dryers in all the restrooms.
→Compared_with_paper_towels,_hand_dryers_have_more_advantages,_which_will_benefit_our_school_in_four_ways.
2．First of all, the automatic hand dryer is very sanitary(卫生的).No bacteria can get on them because there is nothing to touch.
→First,_they_are_clean_and_healthy_because_bacteria_can't_touch_kids.
3．When people dry their hands for at least 30 seconds, automatic dryers actually dry much better than paper towels.It is difficult to get every part of your hand dry using paper towels, but the air can if you take a few extra seconds.
→Besides,_it_can_dry_our_hands_more_effectively_if_we_take_longer_time.
4．As you see there are some good points, let's install automatic hand dryers as soon as possible.
→Therefore,_the_school_is_advised_to_fix_the_equipment_at_once.
5．You can obtain a large amount of information on the Internet nowadays.
→Abundant_information_is_available_on_the_Internet.
Ⅰ.阅读理解
语篇类型 夹叙夹议文
主题语境 人与自然——医学研究——已知的和未知的事物
(2020·江苏高考·D)I was in the middle of the Amazon (亚马逊) with my wife, who was there as a medical researcher.We flew on a small plane to a faraway village.We did not speak the local language，did not know the customs，and more often than not，did not entirely recognize the fooD．We could not have felt more foreign.
We were raised on books and computers，highways and cell phones，but now we were living in a village without running water or electricity.It was easy for us to go to sleep at the end of the day feeling a little misunderstooD．
Then one perfect Amazonian evening，with monkeys calling from beyond the village green，we played soccer.I am not good at soccer，but that evening it was wonderful.Everyone knew the rules.We all spoke the same language of passes and shots.We understood one another perfectly.As darkness came over the field and the match ended，the goal keeper，Juan，walked over to me and said in a matter of fact way，“In your home，do you have a moon too？” I was surpriseD．
After I explained to Juan that yes，we did have a moon and yes，it was very similar to his，I felt a sort of awe (敬畏) at the possibilities that existed in his worlD．In Juan's world，each village could have its own moon.In Juan's world，the unknown and undiscovered was vast and marvelous.Anything was possible.
In our society，we know that Earth has only one moon.We have looked at our planet from every angle and found all of the wildest things left to finD．I can，from my computer at home，pull up satellite images of Juan's village.There are no more continents and no more moons to search for，little left to discover.At least it seems that way.
Yet，as I thought about Juan's question，I was not sure how much more we could really rule out.I am，in part，an ant biologist，so my thoughts turned to what we know about insect life and I knew that much in the world of insects remains unknown.How much，though How ignorant(无知的) are we The question of what we know and do not know constantly bothered me.
I began collecting newspaper articles about new species，new monkey，new spider...，and on and on they appear.My drawer quickly filleD．I began a second drawer for more general discoveries: new cave system discovered with dozens of nameless species，four hundred species of bacteria found in the human stomach.The second drawer began to fill and as it did，I wondered whether there were bigger discoveries out there，not just species，but life that depends on things thought to be useless，life even without DNA．I started a third drawer for these big discoveries.It fills more slowly，but all the same，it fills.
In looking into the stories of biological discovery，I also began to find something else，a collection of scientists，usually brilliant，occasionally half mad，who made the discoveries.Those scientists very often see the same things that other scientists see，but they pay more attention to them，and they focus on them to the point of exhaustion (穷尽)，and at the risk of the ridicule of their peers.In looking for the stories of discovery，I found the stories of these people and how their lives changed our view of the worlD．
We are repeatedly willing to imagine we have found most of what is left to discover.We used to think that insects were the smallest organisms (生物)，and that nothing lived deeper than six hundred meters.Yet，when something new turns up，more often than not，we do not even know its name.
文章大意：本文是一篇夹叙夹议文。作者介绍了自己通过与在亚马逊雨林中生活的当地人的接触中，发现一些人对外部的世界并不了解。作者意识到，很多东西是人类已知的，还有很多是人类未知的。
1．How did the author feel on his arrival in the Amazon
A．Out of place. B．Full of joy.
C．Sleepy. D．Regretful.
解析：A 推理判断题。根据文章第一段We did not speak the local language，did not know the customs，...did not entirely recognize the fooD．We could not have felt more foreign.可知作者不会说当地语言，不知道当地的风俗，甚至不知道当地的食物，因此作者感觉自己格格不入。A项out of place“格格不入，不相称，不适当”，符合作者的感受。故选A。
2．What made that Amazonian evening wonderful
A．He learned more about the local language.
B．They had a nice conversation with each other.
C．They understood each other while playing.
D．He won the soccer game with the goal keeper.
解析：C 细节理解题。根据文章第三段I am not good at soccer，but that evening it was wonderful.Everyone knew the rules.We all spoke the same language of passes and shots.We understood one another perfectly.可知踢球时他们的彼此理解使得那个亚马逊夜晚很美好。故选C。
3．Why was the author surprised at Juan's question about the moon
A．The question was too straightforwarD．
B．Juan knew so little about the worlD．
C．The author didn't know how to answer.
D．The author didn't think Juan was sincere.
解析：B 推理判断题。根据文章第四段In Juan's world，the unknown and undiscovered was vast and marvelous.可知在Juan的世界里，未知的东西和未被发现的东西是浩瀚而神奇的。可推断出Juan对世界知之甚少。故选B。
4．What was the author's initial purpose of collecting newspaper articles
A．To sort out what we have known.
B．To deepen his research into Amazonians.
C．To improve his reputation as a biologist.
D．To learn more about local cultures.
解析：A 推理判断题。根据文章第七段“a second drawer for more general discoveries”“a third drawer for these big discoveries”可推知作者把所知道的、所发现的进行了归类整理。故选A。
5．How did those brilliant scientists make great discoveries
A．They shifted their viewpoints frequently.
B．They followed other scientists closely.
C．They often criticized their fellow scientists.
D．They conducted in depth and close studies.
解析：D 细节理解题。根据文章第八段Those scientists very often see the same things that other scientists see，but they pay more attention to them，and they focus on them to the point of exhaustion，and at the risk of the ridicule of their peers.可知那些科学家经常看到和其他科学家看到的一样的东西，但他们更加关注这些发现，他们把注意力集中在这些发现上直到精疲力竭的地步，冒着被同行嘲笑的风险。可知杰出科学家的研究更有深度。故选D。
6．What could be the most suitable title for the passage
A．The Possible and the Impossible
B．The Known and the Unknown
C．The Civilized and the Uncivilized
D．The Ignorant and the Intelligent
解析：B 主旨大意题。作者在与亚马逊雨林中生活的当地人的接触中，发现一些人对外部的世界并不了解。作者意识到，很多东西是人类已知的，还有很多是人类未知的。根据文章中的关键词the unknown，what we know and do not know，可知标题应为The Known and the Unknown，故选B。
Ⅱ.完形填空
语篇类型 记叙文
主题语境 人与自我——个人经历——异国求学的暖人故事
(2021·山东部分重点中学新起点摸底联考)This semester, I am studying abroad at Mahidol University in ThailanD．One day, I traveled to Kancheanaburi with two friends.After visiting our last destination, due to the __1__ of local transportation, we decided to take a long walk to the station to __2__ the last bus at 8 p．m. back.
However, when we arrived around 7：20 p．m., we were told by the staff there that we went to the wrong place.We did not even think about __3__ this could happen or where we actually were since the only __4__ then was how to get to the station on time.With no taxi on the road and no bus to the station, we were __5__ there.Seeing our anxiety, the staff said they could help us.The male staffer immediately stopped having his dinner and __6__ the motorcycle engine.However, that motorcycle, as the only transportation they __7__ at that time, could only take one passenger.It would take __8__ 15 minutes for a round trip.
Around 7：40 p．m., I was still there.Suddenly, a young man came to __9__ someone off with a motorcycle.The female staffer, who kept talking with me to alleviate(缓和)my worry, stopped him.After they spoke, he nodded, and she hurried me up to __10__ the motorcycle.I did not know who he was, but I could remember that he seemed as __11__ as I was, like the person who was about to miss the last bus back was him instead of me.He drove fast, which I normally would be afraid of, but I felt __12__ then.With my hands on his shoulder, I believed he would __13__ send me to the station safely.
Everything happened so quickly.It was not until the next day __14__ I knew we mistakenly went to their administrative (行政的)office at first.Although I have said“Thank you”to them several times, I still think it is not enough to express my appreciation.I know who they are now: They are the nameless people who are willing to selflessly help others, __15__love and warmth in society.
文章大意：本文是一篇记叙文，文章主要讲述了作者去泰国做交换生，在温暖的国家遇见温暖的人的故事。
1．A．absence B．number
C．speed D．limitations
解析：D 句意：因为当地交通的有限性，我们决定走远路去车站。absence缺少；number数字；speed 速度；limitations局限。根据后文“we decided to take a long walk to the station...”可知，因为当地交通的有限性，作者他们决定走远路去车站。故选D。
2．A．chase B．grasp
C．catch D．seize
解析：C 句意：因为当地交通的有限性，我们决定走远路去车站，赶上下午8点返回的最后一班车。 chase追赶；grasp抓住；catch赶上；seize抓住。根据 the station可知，空处需用动词catch，catch the bus 赶上车，固定搭配。故选C。
3．A．how B．why
C．when D．what
解析：B 句意：我们甚至都没想为什么会发生这样的事情。 how如何，表示方式；why为何，表示原因；when何时，表示时间；what什么，表示事情。前文中的动词是think about, 思考事情的来龙去脉用why，所以空处需用why引导宾语从句。故选B。
4．A．dilemma B．approach
C．annoyance D．concern
解析：D 句意：因为那时唯一担忧的事是如何准时到达车站。dilemma(进退两难)的困境；approach方法；annoyance 烦恼；concern担心。根据下文“如何到达车站”表达的是人内心的担忧。故选D。
5．A．stuck B．abandoned
C．blocked D．isolated
解析：A 句意：因为路上没有通往车站的出租车和公交车，我们被困在那里了。stuck困住；abandoned抛弃；blocked阻挡； isolated孤立。根据空前“With no taxi on the road and no bus to the station”可知，因为没有出租车和公交车，作者他们被困在了那里。故选A。
6．A．started B．set
C．fired D．launched
解析：A 句意：这个男职员立即停止进餐，发动摩托车。started发动；set设置；fired解雇，开火；launched发射。根据下文“take the passenger”，说明这个人是发动摩托车。故选A。
7．A．paid attention to B．had faith in
C．had a preference for D．had access to
解析：D 句意：当时，摩托车是他们唯一能获取的交通工具。paid attention to注意；had faith in信任；had a preference for 偏爱；had access to获取，得到。空处需用had access to，表示摩托车是他们唯一能获取的交通工具，与前文的“当地交通的限制”意思相吻合。故选D。
8．A．no more than B．less than
C．more than D．more or less
解析：C 句意：全程往返需要15分钟多。 no more than不超过；less than少于；more than多于；more or less或多或少。根据下文7：40了，I was still there.说明一个来回耗时较长。故选C。
9．A．drop B．take
C．leave D．send
解析：A 句意：一个年轻人骑着摩托车让一个人下车。这四个选项都可以和空后介词off构成动词短语。drop off让某人下车；take off脱下；起飞；leave off删除，遗漏；send off 发送。依据前文每次只能载一个人，说明这个人下车后我才能上车。固定搭配drop sB．off.让人下车。故选A。
10．A．get off B．get on
C．get in D．get into
解析：B 句意：她赶紧让我坐上摩托车。get off下车、船、飞机；get on 上车；get in收割，收进来；get into 养成，形成。根据前文有人下车和“After they spoke, he nodded ”可知，此处指她让我赶紧坐上摩托车。故选B。
11．A．frustrated B．annoyed
C．worried D．satisfied
解析：C 句意：他似乎和我一样担心。frustrated 受挫折的；annoyed 恼火的；worried 担心的；satisfied 满意的。依据上下文他跟我一样担心的心情，可知此处需用形容词worried。故选C。
12．A．in belief B．with respect
C．for sure D．at ease
解析：D 句意：他把车开得很快，这是我平常所害怕的，但那时我感到很自在。in belief相信；with respect尊重；for sure肯定；at ease轻松，自在。由转折连词but可知，空处需用at ease与前文 be afraid of 对应，表示感到自由自在。故选D。
13．A．desperately B．directly
C．definitely D．deliberately
解析：C 句意：我相信他一定会把我安全地送到车站。desperately 绝望地，迫切地；directly 直接地；definitely确定无疑地；deliberately故意地。依据上文作者感受到当地人的热情，同时动词believe 进一步表达了作者信任对方的态度。故选C。
14．A．when. B．that
C．which D．before
解析：B 句意：直到第二天我才知道我们一开始走错路了，走到行政办公室了。根据空前“It was not until the next day”可知，空处需用that，It is/was not until...that...“直到……才”，固定句型。故选B。
15．A．sparing B．spreading
C．transforming D．transmitting
解析：B 他们是心甘情愿无私助人的无名人士，在社会上传播爱和温暖。sparing 匀出，腾出，抽出；spreading 传播，传递；transforming转变；transmitting 输送，传输。根据空后“love and warmth in society”可知，此处指的是在社会上传播爱和温暖。故选B。
Ⅲ.概要写作
阅读下面短文，根据其内容写一篇60词左右的内容概要。
In 1971，China's first subway line in Beijing was formally put into operation.By December 2017，there were 171 subway lines stretching over 5，083 km in 35 cities on the Chinese mainlanD．Currently，China has the longest urban railway network in the worlD．
The rapid development of China's urban railway system reflects the country's growing economic strength.The system has experienced the fastest growth over the past 15 years due to the investment of wealth accumulated from the reform and opening up in urban infrastructure construction.An urban railway system is expensive to build，with one kilometer of subway costing approximately 700 million yuan($110 million).A city without economic strength cannot develop such an expensive system.
The progress in urban railway construction technologies has also contributed to the fast expansion of the infrastructure.Subway construction involves building underground tunnels，laying rails，manufacturing trains and the operation and management of subways.It is a systematic project which not only covers traditional infrastructure building but also modern electronics and information technology.China's railway construction technologies are the best in the world，with Chinese subway trains now exported to developed countries including the United States.
The expansion of Chinese cities has made it necessary to develop urban railway systems.Since the start of the reform and opening up，a large number of people have migrated to cities and the number of private cars has increased dramatically，resulting in serious traffic congestion.Building subways has become an important way to solve this problem.
This year marks the 42nd anniversary of the launch of China's reform and opening up，and the rapid development of China's urban railway system exemplifies the achievements made by the policy.As China furthers its opening up，it will continue to maintain steady and rapid economic growth and railway systems will be available in more and more cities.
One possible version
The past few decades has witnessed the fast development of Chinese urban railways both in number and length，which is a reflection of China's prosperous economy.(要点1)Actually，not only the growing construction technologies but also the expansion of Chinese cities with booming population and heavy traffic，stimulates the urban railway construction.(要点2)With the deepening of the reform and opening up policy，more urban railways will come into use.(要点3)
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