1.由that引导
The fact is that he doesn’t really try.事实是他没有做真正的努力。
The trouble is that I have lost his address.麻烦的是我把他的地址丢了。
My suggestion is that we should tell him.我的建议是我们应该告诉他。
2.由whether引导
The question is whether the film is worth seeing.问题是这部电影是否值得看。
3.由连接代词引导
You are not who I thought you were.你已不是我过去所想像的人。
The problem is who we can get to replace her.问题是我们能找到谁去替换她呢。
The question is who we should trust.问题是我们应当相信谁。
What I want to know is which road we should take.我想知道的是我们应走哪条路。
4. 由连接副词引导
The problem is how we can find him. 问题是我们如何找到他。
That was when I was fifteen. 这是我15岁时发生的事。