have you played the piano?-For four years. A How often B How long C How much D How

问题补充：

--- have you played the piano? ---For four years.

A How often B How long C How much D How many

答案：

解析：A.多久一次 B.多长时间 C.多少钱D.多少个句意：你弹了多长时间钢琴？——四年。可知选B。