对since和for提问是用when还是how long

线上365bet注册 admin 2026-06-18 01:42:57

—When did you come here?

—______________.

A. Half an hour before

B. Since half an hour

C. Half an hour ago

D. For half an hour

①请问这道题选A还是C呢？这两个选项又有什么区别呢？

②对since和for提问是用when还是how long？