—are you staying there?—Just for two days. A. How longB. WhenC. How oftenD. How many

问题补充：

—are you staying there?

—Just for two days.

A. How long

B. When

C. How often

D. How many

答案：

(答案→)A. How long

B. When

C. How often

D. How many

解析：本题回答的是时间长度，对此提问的用how long，故选A。When对时间提问，how often对频率提问，how many对数量提问。