What the police want to know is when you entered the room.
The trouble is that we are short of funds. 困難是我們缺乏資金。
This is what we should do. 這是我們應當做的。
That's why I want you to work there. 那就是我要你在那兒工作的原因。
His first question was whether Mr. Smith had arrived yet.
as if, as though, because也可用來引導補語子句
She seems as if she had done a great thing. 她看起來好像做了一件大事。
It is because you eat too much. 那是因為你吃得太多了。
主語是idea, notion, proposal, suggestion, request等名詞時,作補語子句的動詞為原形動詞或
My suggestion is that we (should) go and help him. 我的建議是我們應該去幫助他。
Our only request is that this should be settled as soon as possible.