Unit 8 Detective stories
第2课时 Reading课时练习
一、单项选择
1．I like singing ________ she likes dancing.
A．but B．so C．while D．when
2．________ I was studying in the library, Mike called me.
A．Before B．If C．Because D．While
3．While I ________ my breakfast, the postman came and brought me the newspaper.
A．am having B．was having C．have had D．had
4．________ John was watching sports on TV, his wife was cooking.
A．As B．As soon as C．While D．Until
5．David fell fast asleep while he ________ a newspaper.
A．reads B．has read C．was reading D．is reading
6．Mr Su was driving in the snowstorm ________ his car crashed into a tree.
A．when B．as C．while D．as soon as
7．Yesterday, we were playing football in the playground _________ the heavy rain suddenly started.
A．until B．while C．when D．before
8．Mother was watching TV in the sitting room ________ Jack was reading in his study.
A．if B．as C．when D．while
9．Mary was doing her homework ________ she was listening to music.
A．when B．while C．as D．before
10．While she ________ TV in the sitting room, Mum ________.
A．watches; come in B．is watching; came in
C．was watching; came in D．was watching; was coming in
11．Tom was playing with a toy ________ his sister was drawing a picture.
A．when B．while C．if D．but
12．—What’s the matter, Mary
—As a true friend, I can see the sadness in her eyes, ________ everyone else believes the smile on her face.
A．while B．because C．before D．until
13．While we ________the crops, it suddenly poured with rain.
A．were harvesting B．harvested C．are harvesting D．harvest
14．________ technology(科技) moves forward, we can enjoy the night sky with a pair of small binoculars of a smartphone.
A．When B．Until C．Before D．As
15．________ days went by, Jack grew into a tall young man.
A．As B．When C．While D．Since
16．At noon, I took a photo of some swans while they ________ on the lake.
A．dance B．are dancing C．have danced D．were dancing
17．—What were you doing at this time yesterday
—I ________ the news about Huang Dongping’s visit to her hometown on TV.
A．was watching B．watched C．am watching
18．As the Chinese national flag ________, I was so happy that I cried.
A．was rising B．has risen C．will rise D．rises
19．What ________ you ________ at 6 a.m. yesterday
A．did; do you B．were; doing C．were; do D．does; do
20．—What did Tom say
— He said he ________ a math problem with his teacher on the internet at that time.
A．discusses B．was discussing C．is discussing
21．—I didn’t see you at John’s birthday party last night.
—I ________ so hard on the project at that time.
A．was working B．worked C．am working
22．—What do you plan to do in the coming new year
—Sorry, but what did you say I ________ about something else.
A．think B．thought C．am thinking D．was thinking
23．Mum was cooking when I ________ home.
A．am B．was C．get D．got
24．—Jane, I rang you up last night, but nobody answered.
—Oh, I together with my parents ________ walks in the park.
A．have taken B．was taking C．were taking D．had taken
25．The Blacks ________ lunch when I got to their house.
A．were having B．was having C．are having D．had
二、用所给单词的正确形式填空
26．We （ring）someone to come and help when you saw us.
27．While we (mop) up the floor, the telephone suddenly rang.
28．You could see from his face that he (lie) when he kept blinking (眨眼).
29．He (tie) a sheep to a tree when I saw him.
30．Some crazy fans (wait) for August Cai when we arrived at the airport.
31．The boy (practise) football when I passed by.
32．Bob with his family (watch) a wonderful film when the earthquake happened.
33．The Greens (discuss) something in the living room when I went to visit them yesterday.
34．—I called you at half past nine this morning, but there was no answer.
—Oh, sorry. I (shop) with my cousin in the supermarket.
35．The baby (sleep) while the mother (watch) TV.
36．The earth is covered with thick . It heavily last night and the weather was . It’s still now. (snow)
37．I’m sorry that I didn’t answer your phone. I (listen) to music and didn’t hear the ring.
38．His parents are waiting for him at the train station (nervous).
39．Lucy （dance）while her sister （sing）at 6：00 p.m. yesterday.
40．You should say “thanks” when (accept) a gift.
三、改写句子
41．While we were walking on the road, it began to rain. (用when改写句子)
We were walking on the road began to rain.
42．Betty was cooking when I visited her yesterday. (改为同义句)
Betty yesterday, I visited her.
43．She didn’t come back because she was ill. (改为同义句)
She didn’t come back her illness.
44．While it was raining, the plane landed.（同义句转换）
It was raining the plane landed.
四、汉译英与完成句子。
45．当孩子们到达那里，他们迫不及待地打开了礼物。
46．当我们到达公园时，所有人都等不及下了车。（can’t wait）
47．当我们阅读有趣的书时，时间似乎过得更快。
48．孩子们长大了，父母会时常感到孤独。
49．冬天来了，一些鸟儿要飞往南方过冬。（as）
50．当他醒来的时候，已经十点了。可怜的马丁，上班又迟到了！
, it was already ten o’clock. Poor Martin! Late for work again!Unit 8 Detective stories
第2课时 Reading课时练习
一、单项选择
1．I like singing ________ she likes dancing.
A．but B．so C．while D．when
【答案】C
【详解】句意：我喜欢唱歌，而她喜欢跳舞。
考查连词辨析。but但是；so因此；while而；when当……时候。根据“I like singing ... she likes dancing.”可知前后表对比，用while连接并列句。故选C。
2．________ I was studying in the library, Mike called me.
A．Before B．If C．Because D．While
【答案】D
【详解】句意：当我在图书馆学习时，迈克打电话给我。
考查连词辨析。Before在……之前；If如果；Because因为；While当……时。根据“... I was studying in the library, Mike called me.”可知此处表示当某事正在进行的时候，另一件事情发生了，用While引导时间状语从句。故选D。
3．While I ________ my breakfast, the postman came and brought me the newspaper.
A．am having B．was having C．have had D．had
【答案】B
【详解】句意：当我正在吃早餐时，邮递员给我送来了报纸。
考查过去进行时。根据“While I...my breakfast, the postman came and brought me the newspaper.”可知，主句“the postman came and brought me the newspaper”的时态是一般过去时，而“While I...my breakfast”为由while引导的时间状语从句，从句中的谓语动词为延续性动词have，所以此时从句应用过去进行时，谓语结构是was/were doing，从句的主语是I，此时be动词应用was。故选B。
4．________ John was watching sports on TV, his wife was cooking.
A．As B．As soon as C．While D．Until
【答案】C
【详解】句意：当约翰在看电视上的体育比赛时，他的妻子正在做饭。
考查连词辨析。As因为；As soon as一……就……；While当……时；Until直到。根据“...John was watching sports on TV, his wife was cooking.”可知，主从句的动作同时发生，用while引导时间状语从句。故选C。
5．David fell fast asleep while he ________ a newspaper.
A．reads B．has read C．was reading D．is reading
【答案】C
【详解】句意：大卫在读报纸的时候睡着了。
考查时态的用法。根据“David fell fast asleep while he…a newspaper”可知，while引导时间状语从句，主句用一般过去时，从句用过去进行时，其构成为was/were doing。故选C。
6．Mr Su was driving in the snowstorm ________ his car crashed into a tree.
A．when B．as C．while D．as soon as
【答案】A
【详解】句意：苏在暴风雪中开车时，汽车撞到了树上。
考查连词辨析。when当；as随着；while当；as soon as一……就。根据“Mr Su was driving in the snowstorm...his car crashed into a tree.”可知是当车撞到树上时，crash是非延续性动词，不能用while，而as强调一件事情正在发生，另一件事也正在进行当中，不符合语境。故选A。
7．Yesterday, we were playing football in the playground _________ the heavy rain suddenly started.
A．until B．while C．when D．before
【答案】C
【详解】句意：昨天，我们正在操场上踢足球，突然下起了大雨。
考查连词辨析。until直到；while在……期间，表达一个“时间段”，不能表达“时间点”，从句的动词只限于持续性动词；when当……时，多指“时间点”；before之前。be doing...when...表示“正在做某事时另外一件事发生”。故选C。
8．Mother was watching TV in the sitting room ________ Jack was reading in his study.
A．if B．as C．when D．while
【答案】D
【详解】句意：妈妈在客厅看电视，杰克在书房看书。
考查从属连词词义辨析。if如果；as当……时；when当……的时候；while当……的时候。分析“Mother was watching TV in the sitting room...Jack was reading in his study.”可知，主从句是同时进行的持续性动作，应用while引导时间状语从句。故选D。
9．Mary was doing her homework ________ she was listening to music.
A．when B．while C．as D．before
【答案】B
【详解】句意：玛丽一边听音乐一边做作业。
考查连词辨析。when当……时；while当……时；as随着；before在……之前。根据“Mary was doing her homework”和“she was listening to music.”可知，两句都用过去进行时态，且是同时进行的持续性动作，应用while引导时间状语从句。故选B。
10．While she ________ TV in the sitting room, Mum ________.
A．watches; come in B．is watching; came in
C．was watching; came in D．was watching; was coming in
【答案】C
【详解】句意：当她在客厅看电视的时候，妈妈进来了。
考查while引导的时间状语从句。while引导的时间状语从句，从句通常是延续性动词，且表示过去正在发生的事情，则应用过去进行时态，其结构是“was/were doing”，则第一空应填was watching；come“来”，短暂性动词，主句用一般过去时，动词应用过去式，则第二空应填写came in。故选C。
11．Tom was playing with a toy ________ his sister was drawing a picture.
A．when B．while C．if D．but
【答案】B
【详解】句意：汤姆在玩玩具，而他妹妹在画画。
考查连词。when当……时，引导时间状语从句时，主句用过去进行时，从句应用一般过去时；while当……的时候，引导时间状语从句时，主从句通常都用过去进行时；if如果；but但是。根据语境可知，此处表示两个动作同时发生，故应用while引导时间状语从句，故选B。
12．—What’s the matter, Mary
—As a true friend, I can see the sadness in her eyes, ________ everyone else believes the smile on her face.
A．while B．because C．before D．until
【答案】A
【详解】解析：句意：——怎么了，玛丽？——作为一个真正的朋友，我能看到她眼中的悲伤，而其他人都相信她脸上的微笑。
考查从属连词辨析。while当……的时候，引导时间状语从句；because因为，引导原因状语从句；before在……的前，引导时间状语从句；until直到……为止，引导时间状语从句。根据句意，当所有人相信她脸上的笑容时，真正的朋友可以看到她眼中的痛苦。表示“当……的时候”，故选A。
13．While we ________the crops, it suddenly poured with rain.
A．were harvesting B．harvested C．are harvesting D．harvest
【答案】A
【详解】句意：当我们正在收庄稼的时候, 天突然下起了雨。
考查过去进行时。句中while表示“当……时候”,与之连用的时态为进行时态，故可排除B和D选项；根据后半句的动词poured是过去式形式,可推断事情发生在过去。故设空处应用过去进行时“were harvesting”。故选A。
14．________ technology(科技) moves forward, we can enjoy the night sky with a pair of small binoculars of a smartphone.
A．When B．Until C．Before D．As
【答案】D
【详解】句意：随着科技的进步，我们可以用智能手机的双筒望远镜欣赏夜空。
考查时间状语从句。When当……时；Until直到；Before在……之前；As随着。根据句意可知，此处表示伴随状态，随着科技进步，我们可以更智能地欣赏夜空。故选D。
15．________ days went by, Jack grew into a tall young man.
A．As B．When C．While D．Since
【答案】A
【详解】句意：随着日子一天天过去，杰克长成了一个高大的年轻人。
考查连词辨析。As随着；When当……时；While当……时；Since自从。根据“…days went by”可知，此处指随着日子一天天过去，用as引导时间状语从句，故选A。
16．At noon, I took a photo of some swans while they ________ on the lake.
A．dance B．are dancing C．have danced D．were dancing
【答案】D
【详解】句意：中午，当天鹅在湖上跳舞时我拍了些照片。
考查过去进行时。根据while和took可知，要用过去进行时，表示过去某一时刻正在做某事，D项符合题意。故选D。
17．—What were you doing at this time yesterday
—I ________ the news about Huang Dongping’s visit to her hometown on TV.
A．was watching B．watched C．am watching
【答案】A
【详解】句意：——昨天这个时候你在做什么 ——我正在电视上看黄东平回老家的新闻。
考查动词时态。根据“What were doing this yesterday... ”可知，答语需用过去进行时，过去进行时的构成是：was/were+doing。主语是I，be动词用was，动词watch的现在分词是watching。故选A。
18．As the Chinese national flag ________, I was so happy that I cried.
A．was rising B．has risen C．will rise D．rises
【答案】A
【详解】句意：当中国国旗升起的时候，我高兴得哭了。
考查时态。根据“I was so happy that I cried.”可知，此处讲述过去发生的事情，且强调国旗正在升起时，“我”高兴得哭了，应用过去进行时，结构为was/were doing。故选A。
19．What ________ you ________ at 6 a.m. yesterday
A．did; do you B．were; doing C．were; do D．does; do
【答案】B
【详解】句意：昨天早上6点你在做什么？
考查时态。根据“at 6 a.m. yesterday”可知，时态应用过去进行时，表示过去某一刻正在做什么，结构为was/were doing。故选B。
20．—What did Tom say
— He said he ________ a math problem with his teacher on the internet at that time.
A．discusses B．was discussing C．is discussing
【答案】B
【详解】句意：——汤姆说了什么？——他说当时他正在网上和老师讨论一道数学题。
考查动词时态。discusses一般现在时；was discussing过去进行时；is discussing现在进行时。根据“at that time”可知，此处应用过去进行时。故选B。
21．—I didn’t see you at John’s birthday party last night.
—I ________ so hard on the project at that time.
A．was working B．worked C．am working
【答案】A
【详解】句意：——昨晚聚会开始时我没看到你。——那个时候我在努力做这个项目。
考查时态。根据“at that time”可知，回答聚会开始时在做什么，应用过去进行时。其结构是was/were doing。故选A。
22．—What do you plan to do in the coming new year
—Sorry, but what did you say I ________ about something else.
A．think B．thought C．am thinking D．was thinking
【答案】D
【详解】句意：——在新的一年里你打算做什么？——对不起，你刚才说什么？我在想别的事。
考查时态。根据“Sorry, but what did you say I ... about something else.”可知，你说了什么，我刚刚在想别的事情；表示过去某一刻正在做某事应用过去进行时，结构为was/were doing。故选D。
23．Mum was cooking when I ________ home.
A．am B．was C．get D．got
【答案】D
【详解】句意：我到家时我妈妈正在做饭。
考查when引导的时间状语从句。am是，修饰主语I，一般现在时；was是，am和is的过去式，一般过去时；get得到，到达，一般现在时；got得到，到达，一般过去时。when引导的状语从句表示时间，说明一个动作发生时，另一个动作正在进行。结合“was cooking”可知，此处为一般过去时，应用get的过去式，构成“got home回家”，符合语境。故选D。
24．—Jane, I rang you up last night, but nobody answered.
—Oh, I together with my parents ________ walks in the park.
A．have taken B．was taking C．were taking D．had taken
【答案】B
【详解】句意：——Jane，昨晚我打电话给你，但是没人接听。——哦，我那时正和父母在公园散步。
考查时态和主谓一致。根据“I rang you up last night, but nobody answered.”可知昨晚电话没人接听，所以那时Jane正在散步，故用过去进行时，谓语结构是was/were doing，且together with连接两个并列主语时遵循“就远原则”，be动词的数和I保持一致，此时用was。故选B。
25．The Blacks ________ lunch when I got to their house.
A．were having B．was having C．are having D．had
【答案】A
【详解】句意：我到布莱克家时，他们正在吃午饭。
考查时态。根据“The Blacks...lunch when I got to their house.”可知，句子为when引导的时间状语从句，此处表示某一动作发生的时候，另一件事情正在进行，主句是持续性动作，从句用一般过去时，主句用过去进行时。故选A。
二、用所给单词的正确形式填空
26．We （ring）someone to come and help when you saw us.
【答案】were ringing
【详解】句意：当你看到我们时，我们正在给某人打电话来帮忙。根据“when you saw us”可知看见我们的时候，我们正在打电话，用过去进行时，主语是we，be动词用were。故填were ringing。
27．While we (mop) up the floor, the telephone suddenly rang.
【答案】were mopping
【详解】句意：当我们正在拖地板时，电话铃突然响了。根据“While we...up the floor, the telephone suddenly rang.”可知，强调在过去的某个时刻正在发生的动作，应使用过去进行时，故填were mopping。
28．You could see from his face that he (lie) when he kept blinking (眨眼).
【答案】was lying
【详解】句意：他不停地眨眼睛，从他脸上你可以看出他在说谎。分析语境可知，这里指的是“他脸上的表情”说明“在撒谎”，所以空处用进行时，结合“could”和“kept ”可知，此处用过去进行时，主语是he，be动词用was，lie的现分词是lying。故填was lying。
29．He (tie) a sheep to a tree when I saw him.
【答案】was tying
【详解】句意：当我看到他时，他正在把一只羊绑在树上。根据“when I saw him”在此处是when引导的时间状语从句，主句用过去进行时，从句为一般过去时。主语“He”为第三人称单数，谓语用was，tie的现在分词为tying。故填was tying。
30．Some crazy fans (wait) for August Cai when we arrived at the airport.
【答案】were waiting
【详解】句意：当我们到达机场时一些疯狂的粉丝正在等蔡徐坤。根据“when we arrived at the airport.”可知此处时态为过去进行时，其谓语结构为“was/were+doing”，主语fans为复数，be动词应用were，故填were waiting。
31．The boy (practise) football when I passed by.
【答案】was practising
【详解】句意：我经过时，那个男孩正在练习足球。根据“…when I passed by.”可知，此处表达过去某一时刻正在发生的动作，用过去进行时，其构成是was/were doing，practise的现在分词形式是practising，主语是第三人称单数，be动词用was。故填was practising。
32．Bob with his family (watch) a wonderful film when the earthquake happened.
【答案】was watching
【详解】句意：当地震发生时，鲍勃和家人正在看一部精彩的电影。根据“when the earthquake happened.”可知，此处是when引导的时间状语从句，从句是一般过去时态，主句用过去进行时，其结构是was/were doing的形式，主语是Bob是第三人称单数，be动词用was，watch“看”，现在分词是watching，故填was watching。
33．The Greens (discuss) something in the living room when I went to visit them yesterday.
【答案】were discussing
【详解】句意：昨天我去拜访格林一家时，他们正在客厅里讨论一些事情。根据“when I went to visit them yesterday”可知，此处强调在过去的某个时间点正在发生的动作，用过去进行时，主语是复数，be动词用were。故填were discussing。
34．—I called you at half past nine this morning, but there was no answer.
—Oh, sorry. I (shop) with my cousin in the supermarket.
【答案】was shopping
【详解】句意：——我早上9点半给你打电话，但是你没接。——喔，抱歉。我正和我表哥在超市买东西呢。根据上文“I called you at half past nine this morning”可知，双方在讨论上午9点半这个具体时刻所发生的的事情。所以下文应使用过去进行时回答，表示在上午9点半，正在超市购物。过去进行时的结构为was/were + doing，主语是I，所以用was，shop需要双写加ing。故填was shopping。
35．The baby (sleep) while the mother (watch) TV.
【答案】 is sleeping/was sleeping is watching/was watching
【详解】句意：婴儿在睡觉的时候，妈妈在看电视。根据while及括号内提示词可知，婴儿和妈妈发生的动作是同时进行的，sleep和watch均属于可延续性动词，所以都应使用进行时。该句没有明确的时间状语，所以现在进行时和过去进行时均可以。“The baby”和“the mother”都是第三人称单数，所以be应使用is或was，sleep和watch变为sleeping和watching。故填is/was sleeping；is/was watching。
36．The earth is covered with thick . It heavily last night and the weather was . It’s still now. (snow)
【答案】 snow snowed snowy snowing
【详解】句意：地球被厚厚的雪覆盖。昨天晚上雪下得很大，天气下着雪。现在仍然在下雪。根据句意可知，第一个空用名词形式，thick形容词，修饰名词snow；第二个空根据last night可知是过去时态，这里缺少谓语动词，所以填snowed；第三个空用形容词作表语，所以填snowy；第四个空根据now可知是现在进行时态，应填snowing。故填snow；snowed；snowy；snowing。
37．I’m sorry that I didn’t answer your phone. I (listen) to music and didn’t hear the ring.
【答案】was listening
【详解】句意：抱歉我没有接到你的电话。我正在听音乐，没有听到铃声。listen“听”，动词。根据“I’m sorry that I didn’t answer your phone.”可知，此处指过去某时动作正在进行，应用过去进行时：was/were+现在分词。主语为I，则助动词为was。故填was listening。
38．His parents are waiting for him at the train station (nervous).
【答案】nervously
【详解】句意：他的父母在火车站紧张地等他。nervous“紧张的”，是形容词，此处应该用其副词形式修饰动词，故填nervously。
39．Lucy （dance）while her sister （sing）at 6：00 p.m. yesterday.
【答案】 was dancing was singing
【详解】句意：昨天下午六点露西在跳舞，她的姐姐在唱歌。此句是while引导的时间状语从句，表示主句和从句动作同时发生，句子应该用过去进行时，即was/were+V-ing。主语Lucy和her sister 均为第三人称单数，故be动词用was。故填was dancing；was singing。
40．You should say “thanks” when (accept) a gift.
【答案】accepting
【详解】句意：当你接受礼物时说“谢谢”是礼貌的。此句是when引导的时间状语从句，主从句主语一致，且从句含有be动词，此时可将从句主语和be动词省略。故填accepting。
三、改写句子
41．While we were walking on the road, it began to rain. (用when改写句子)
We were walking on the road began to rain.
【答案】 when it
【详解】句意：当我们走在路上时，天开始下雨了。原句是while引导的时间状语从句，可换为when引导的时间状语从句，表示“当某事发生的时候，另一件事正在进行”，从句中用短暂性动作，it后用began。故填when；it。
42．Betty was cooking when I visited her yesterday. (改为同义句)
Betty yesterday, I visited her.
【答案】 While/When was cooking
【详解】句意：我昨天看望她的时候，她正在做饭。根据原句“Betty was cooking when I visited her yesterday.”和其同义句“...Betty...yesterday, I visited her.”可知，在同义句中，主句“I visited her”是一般过去时，则时间状语从句应是“Betty was cooking”，从句时态为过去进行时，此时从句可用while/when来引导。故填While/When；was；cooking。
43．She didn’t come back because she was ill. (改为同义句)
She didn’t come back her illness.
【答案】 because of
【详解】句意：她没有回来，因为她病了。because引导的原因状语从句可改为“because of+名词性短语”。becuase of“因为”。故填because；of。
44．While it was raining, the plane landed.（同义句转换）
It was raining the plane landed.
【答案】when
【详解】句意：下雨时，飞机降落了。此处可以用when“当……时”引导时间状语从句，表示“当飞机降落的时候，正在下雨”，故填when。
四、汉译英与完成句子。
45．当孩子们到达那里，他们迫不及待地打开了礼物。
【答案】When the children got/reached/arrived there, they couldn’t wait to open the presents.
【详解】when“当……时候”；children“孩子们”；get/reach/arrive there“到达那里”；they“他们”；can’t wait to do“迫不及待做某事”；open the presents“打开礼物”。分析句子可知，描述的是过去的事情，应该用一般过去时，动词用过去式。故填When the children got/reached/arrived there, they couldn’t wait to open the presents.
46．当我们到达公园时，所有人都等不及下了车。（can’t wait）
【答案】When we got to the park, all of us couldn’t wait to get off the bus.
【详解】当……时：when；到达公园：get to the park；所有人：all of us；等不及：can’t wait to do；下车：get off the bus；结合语境可知，此处应用一般过去时，动词应用过去式。故填When we got to the park, all of us couldn’t wait to get off the bus.
47．当我们阅读有趣的书时，时间似乎过得更快。
【答案】Time seems to go faster when we are reading/read interesting books.
【详解】分析句子可知，句子是when引导的时间状语从句，我们：we，在从句中作主语，阅读：are reading/read，可以用现在进行时或者一般现在时；有趣的书：interesting books，作宾语；时间：Time，作主语；似乎：seem to；过得更快：go faster。故填Time seems to go faster when we are reading/read interesting books.
48．孩子们长大了，父母会时常感到孤独。
【答案】As children grow up, parents often feel lonely.
【详解】根据汉语意思可知此处用as引导时间状语从句，“孩子们”children；“长大”grow up；“父母”parents；“时常”often；“感到孤独”feel lonely。句子陈述一般事实，用一般现在时。故填As children grow up, parents often feel lonely.
49．冬天来了，一些鸟儿要飞往南方过冬。（as）
【答案】As winter comes, some birds want to fly south for the winter.
【详解】根据题干，可知考查：as当……时，引导时间状语从句；winter冬天，作主语时，谓语动词用三单形式；come来；some birds一些鸟儿；want to do sth想做某事；fly south for the winter飞往南方过冬。由句意可知时态是一般现在时，主句主语是复数，接动词原形。故填As winter comes, some birds want to fly south for the winter.
50．当他醒来的时候，已经十点了。可怜的马丁，上班又迟到了！
, it was already ten o’clock. Poor Martin! Late for work again!
【答案】When he woke up/As he woke up
【详解】当……时候when/as，引导时间状语从句；他he，作主语；醒来wake up。根据句意可知，动作发生在过去，时态是一般过去时，动词用过去式，故填When/As he woke up。
