do you exercise ?A. How oftenB. How soonC. How longD. How many

问题补充：

do you exercise ?

A. How often

B. How soon

C. How long

D. How many

答案：

(答案→)A. How often

B. How soon

C. How long

D. How many

解析：根据题意可知选择how often表示多久一次，用询问频率。