— do you go to the cinema?—Once a month.A. How longB. How manyC. How muchD. How often

问题补充：

— do you go to the cinema?

—Once a month.

A. How long

B. How many

C. How much

D. How often

答案：

A. How long

B. How many

C. How much

(答案→)D. How often

解析：A. How long多长； B. How many 多少，提问可数名词数量；C. How much多少，提问不可数名词数量；D. How often多久一次，提问频率，根据答语 Once a month.（一月一次）可知问句是问多久一次，故选D。