《名词性从句之表语从句的使用》 高三三轮冲刺复习
(考点精讲·易错突破·真题实战)
一、表语从句的定义与位置
表语从句(Predicative Clause)属于名词性从句的一种,在句中充当表语,位于系动词(如be, seem, appear, remain等)之后,对主语进行补充说明。其基本结构为:
主语 + 系动词 + 连接词 + 表语从句
例句:
The problem is that we lack enough time.
What surprised me was how he solved the problem quickly.
二、表语从句的三大连接词
1. 连接词 that
功能:仅起连接作用,无实际意义,且不可省略。
例句:
The truth is that he didn’t tell a lie.
My suggestion is that we should start early.
2. 连接词 whether
功能:表示“是否”,不可用 if 替换(表语从句中只用 whether)。
例句:
The question is whether they can finish the task on time.
His doubt is whether the plan will work.
3. 疑问词(what, when, where, why, how, who, whom, whose)
功能:在从句中充当成分(主语、宾语、状语等),有实际含义。
例句:
That is why I refused the offer. (why 作原因状语)
The key point is what we should do next. (what 作宾语)
三、表语从句的特殊用法与注意事项
1. 虚拟语气在表语从句中的使用
当主语为表示“建议、要求、命令”的名词(如 suggestion, advice, order)时,表语从句需用 “(should) + 动词原形” 的虚拟语气结构。
例句:
My advice is that you (should) apologize to her.
The order was that all soldiers (should) stay alert.
2. 表语从句中的 “as if/as though”
表示“好像”时,可用 as if/as though 引导表语从句,从句中根据语境选择陈述语气或虚拟语气。
例句:
It looks as if it is going to rain. (陈述语气,可能真实)
He talked as though he had known everything. (虚拟语气,与事实相反)
3. 表语从句与 “because” 的灵活使用
在强调句型或口语中,可用 because 引导表语从句,但需注意逻辑合理性。
例句:
The reason he was late is because his car broke down. (口语化表达)
对比正式表达:The reason he was late is that his car broke down.
四、表语从句的易错点与解题技巧
易错点1:混淆 that 与 what
错误:The difficulty is that we need to solve.
修正:The difficulty is what we need to solve. (what 在从句中作宾语,that 无实际意义且不充当成分)
易错点2:误用 if 替代 whether
错误:The question is if he will come.
修正:The question is whether he will come.
易错点3:忽略虚拟语气
错误:His suggestion is that we will reduce costs.
修正:His suggestion is that we (should) reduce costs.
五、高考真题实战演练
例题1(2023年新高考I卷):
The reason why he failed the exam was ______ he spent too much time playing games.
A. because B. that C. why D. what
答案:B
解析:表语从句中正式表达用 “that”,避免重复 “reason...because” 的逻辑错误。
例题2(2022年全国甲卷):
What the teacher emphasized was ______ we should review the key points.
A. if B. whether C. that D. what
答案:C
解析:表语从句中需用 that 引导,强调内容。
六、巩固练习与总结
练习1:用表语从句合并句子
The problem is this. How can we protect the environment
→ The problem is how we can protect the environment.
练习2:改错
His idea is if we can find a cheaper solution.
→whether
总结口诀:
表语从句跟系动,连接词要记心中;
that 无义 whether 疑,疑问词在句中用;
虚拟语气别遗漏,易错点要练贯通!