在主语从句中,主句的谓语动词用单数吗

1,what 引导的主语从句作主语时,谓语的数由后面的表语或宾语确定.例如：
What she said is correct.
What he gave me are five English books.
2,其它词引导的名词性从句作主语时,谓语用单数.例如：
Who is responsible for the accidents is not clear.