— do you swim? —Twice a week. A. How long B. How many times C. What time D. How often

问题补充：

— do you swim? —Twice a week.

A. How long

B. How many times

C. What time

D. How often

答案：

A. How long

B. How many times

C. What time

(答案→)D. How often

解析：回答语表示的是频率，对此提问的用how often，故本题选D。