疑问词 when, where, who, what, how
1.He bought three books yesterday
Who bought three books yesterday
What did he buy yesterday
When did he buy three books
how long, how far, how often, why
1. They have been in China for three years
How long have they been in China?
2. It is about 4 kilometers from Beijing to Xi'an
How far is it from Beijing to xi'an?
3. They come to visit me once a week
How often do they come to visit me?
4. She came late, because she missed the bus.
Why did she come late?