一、主语从句：从句作主语谓语动词用单数形式

Whoever says that is wrong.无论谁说这话都不对。

That he will come is certain.他肯定会来。

Whether he has signed the contract or not doesn’t matter.

他是否在合同上签了字，是无关紧要的。

Why he is late for class is more than I can tell.为什么他上课迟到，我也说不上来。