问题补充：
--are the Olympic Games held?
--Every four years.
A. How often
B. How soon
C. How long
D. When
答案：
(答案→)A. How often
B. How soon
C. How long
D. When
解析：考查短语辨析。How often多久一次，表示频率，How soon多久，How long多长，When当什么时候，根据答语内容-Every four years.，可知问句内容为奥运会多久举行一次？故选A
