do you go to the library.I usually go to the library twice a week.A. How longB. How oftenC

问题补充：

do you go to the library.I usually go to the library twice a week.

A. How long

B. How often

C. How far

D. How many

答案：

A. How long

(答案→)B. How often

C. How far

D. How many

解析：句意：你多长时间去一次图书馆？通常一周两次。how long 多长时间，提问时间段；how often 多长时间一次，提问频率；how far多远 ，提问距离；how many多少，提问可数名词的数量，故选B。