12.2 主语从句
（1）用that引导的句子作主语时，不论是否用it先行，谓语动词总是用单数。
That the plates are moving is not beyond dispute.
That our environment has little，if anything，to do with our a bilities，characteristics and behavior is central to this theory.
（2）用wh-型词引导的句子作主语时，谓语动词用单数；但如果用and把两个wh-型从句连接起来作主语，那么谓语就应用复数了。
It’s still a mystery by whom she was kidnapped.
Whether such a sense of fairness stems from the common ancestor that the species had 35 million years age is，as yet，an unanswered question.
It’s hard to say which plan is more practicable.
Where they should go and what they have to do next are difficult to solve.
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