1. 我是在街上遇见她的父亲的。(强调在街上) 2. 你是8点开始工作的吗？（强调时间） 3. 正是因为她病了，他们才没见她做这项工作。 4. 他为什么不能回答这个问题？

It was in the street that I met her father.

Was it at eight o’clock that you began to work?

Because she was ill, they didn’t ask her to do the job. →It was because she was ill that they didn’t ask her to do the job.

Why was it that he couldn’t answer the question.

（强调原因）