-- do you have an English party?-Once a month.A. How old B. How far C. How often D.

问题补充：

---- do you have an English party?

---- Once a month.

A. How old

B. How far

C. How often

D. How long

答案：

A. How old

B. How far

(答案→)C. How often

D. How long

解析：once a month表示一月一次，表示频率，故用how often来提问。