—do you have an Art Festival in your school? —Once a year.A. How long B. How often　C. 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：句意：——你们学校多久举办一次艺术节。—— 一年一次。从回答中可知道问的是频率，多久一次，故选B。 how long多久，how far多远，how soon多快。