—do you have a class meeting?— Once a week.A. How longB. How oftenC. How soonD. When

问题补充：

—do you have a class meeting?

— Once a week.

A. How long

B. How often

C. How soon

D. When

答案：

A. How long

(答案→)B. How often

C. How soon

D. When

解析：How long多长；How often多久一次；How soon多久；When什么时候。根据下文，每周一次。可知上文问的是，你们多久开一次班会？故选B。