---do you go to the cinema?---Once a month.A. How longB. How farC. How oftenD. How much

问题补充：

---do you go to the cinema?

---Once a month.

A. How long

B. How far

C. How often

D. How much

答案：

A. How long

B. How far

(答案→)C. How often

D. How much

解析：How long多长；How far多远；How often多久一次；How much多少钱。根据下文，一个月一次。可知上文提问的是频率，故选C，你多久去一次电影院？