语法拓展

表语从句

表语从句在句子中充当表语，其功能是说明或解释主语。表语从句一定要用陈述语序，且引导词不能省略。

1）表语从句的系动词除 be 之外，还有 look, seem, appear, sound, taste, feel, remain 等。例如：He has become what he wanted to be ten years ago. 他已经成为了十年前他想成为的样子。

2）表语从句的引导词包括：连词 that, whether( that 不能省略，whether 不可以用 if 来替换)；连接代词等 what, whatever, who, whoever 等；连接副词 when, where, how, why 等，一些从属连词和词组如 because, as, as if, as though。例如：But it's not as if earlier times didn't know perpetual war, disaster and the message of innocents. 但这不是说以前的时代没有经历过连续不断的战争、灾难和滥杀无辜。

3）需要注意的是，当句子主语是 reason 时，表语从句应当由 that 而不是 because 来引导，且 that 可省略；但可以用“it/this/that is because...”来表示原因。例如：The reason is that modern man seems unable to redesign his institutions fast enough to accommodate the new demands, the new intelligence, the new abilities of segments of society which, heretofore, have not been taken seriously. 原因在于，现代人似乎不能尽快地修正其已形成的各种习俗以适应那些迄今尚未被认真对待的、来自社会各阶层的新的需求、新的智慧和新的才干。