— do you have an Art Festival in your school? — Once a year.A. How longB. How oftenC. How

问题补充：

— do you have an Art Festival in your school? — Once a year.

A. How long

B. How often

C. How far

D. How soon

答案：

A. How long

(答案→)B. How often

C. How far

D. How soon

解析：四个选项分别表示多长、多久一次，问频率、多远和多久。根据答语每年一次,选B.