【2016年高考北京卷】

29. The most pleasant thing of the rainy season is ________ one can be entirely free from dust.

A. what B. that C. whether D. why

【答案】B

【解析】

试题分析：题目考查表语从句。句意：雨季最令人愉悦的就是人们可以完全不再受沙尘的困扰。is后跟从句作表语，即表语从句，表语从句不缺少主语、谓语和宾语，因此用that,that只起引导作用，故选B。
考点：考查表语从句

【名师点睛】

表语从句 Predictive Clauses (在be动词 后)

1. 从句的连接词可以是that, 也可以是wh-的特殊疑问词。

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The fact is that she never liked him.

The question is whether the movie is worth seeing.

The question is who can complete the difficult task.

u This/That/It is because …

I think it is because you are doing too much.

u The reason why…is that…

The reason why the play is successful is that it appeals to many different people.

2. 只能用whether 的情况

* 在表语从句、主语从句、同位语从句中

* 在介词后的宾语从句中

It all depends on whether they will support us.

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* 在不定式之前

He doesn’t know whether to stay or not.

* 从句中有or not时

He doesn’t know whether he should stay or not.