—do you surf the Internet Kate?— Not often twice a month.A. How longB. How oldC. How oft

问题补充：

—do you surf the Internet, Kate?— Not often, twice a month.

A. How long

B. How old

C. How often

D. How many times

答案：

A. How long

B. How old

(答案→)C. How often

D. How many times

解析：本题的回答语表示的是频率，对此提问用how often，故本题选C。