Question

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

A．How long

B．How often

C．How far

D．How soon

Answer 1

B

解析根据答语once a year可知问的是频度，how often多久一次符合题意，故选B。how long问的是时间或物体的长度；how far问的是距离；how soon问还过多久，都不对。