Asking why with "zenme"
As well as with the question word 为什么, questions can also be asked with 怎么. The structure for this is:
Subject + 怎么 + Verb + Object
This has similar connotations to saying "how come" in English. It not only asks why, but expresses some surprise at the situation, and in some cases even disagreement with it.
Some examples:
- 你 怎么 没 来?
- 你的 汉语 怎么 那么 好?
- 他 怎么 离开 了?