--How often do you drop your English teacher a line?-. But usually once a week.A. As us

问题补充：

--How often do you drop your English teacher a line?

---. But usually once a week.

A. As usual

B. It depends

C. Generally speaking

D. Have no idea

答案：

A. As usual

(答案→)B. It depends

C. Generally speaking

D. Have no idea

解析：情景交际。A. 想玩常一样 B. 看情况而定 C. 总的来说 D. 不知道。句意：你多久给你的英语老师写一封信？——看情况而定。但是通常每周一次。故选B。