主语从句做主语,主句谓语动词的单复数需根据从句表示的单复数意义决定。 1.what引导的主语从句做主语 (1)通常情况下,由what引导的主语从句放在句首时,其后的谓语动词,按语法一致的原则用单数。eg:What she said is correct. What caused the accident is not clear. (2)当主句中的表语是复数形式,或what从句的谓语动词及其补足语均为复数形式时,主句的谓语动词应用复数。eg:What he gave me are five English books. What are used as chief building materials today are steel and concrete. (3)当what引导的主语从句是一个由and连接的并列结构时,应根据句意确定其表达的单复数意义,然后决定主句谓语动词的单复数形式。 eg:What he says and acts does not concern me. What he says and acts do not agree. What I say and what I think are no business of yours. 2.由其它词引导的从句做主语时,谓语动词用单数形式。 Whether they will hold a party or not has not been decided. Who is responsible for the accidents is not clear. 3.当同一个主语从句是由两个不同的引导词引导时,因为它表达的还是同一件事,因此,谓语动词一般用单数。 eg:When and where we should hold the meeting has not been decided yet. 4.当主语是由两个由and连接的主语从句组成,通常表示的是两件不同的事情,主句谓语动词需用复数形式。 What you eat and how much you exercise are important factors in a weight loss program. What caused the accident and who was responsible for it remain a mystery to us. 本文来源：https://www.wddqw.com/doc/f1a27d4b986648d7c1c708a1284ac850ad0204f0.html