The children should be taught when the house caught fire.为什么填what to do,不填how to do it?

题目

The children should be taught when the house caught fire.为什么填what to do,不填how to do it?
The children should be taught--------- when the house caught fire.

答案

此话翻译为：当房屋起火时孩子应该让孩子知道该做什么事.
此处用what to do表示“做什么”的意思.how to do it中it 指代不清,所以不填.