问题补充：
------ are you staying in China?
------For about two months.
A. How far
B. How long
C. How often
D. How many
答案：
A. How far
(答案→)B. How long
C. How often
D. How many
解析：回答语为时间长度，对此提问的通常用how long，故选B.而how far对路程提问，
How often对频率提问，how many对数量提问，故都不选。
