do you help your mother clean the house?- Once a week.A. How farB. How longC. How

问题补充：

--- do you help your mother clean the house?

--- Once a week.

A. How far

B. How long

C. How soon

D. How often

答案：

A. How far

B. How long

C. How soon

(答案→)D. How often

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D。