How long have you been collecting shells?,

问题描述:

How long have you been collecting shells?,
A,After I left school.B,Before I moved here.C,When I went to the beach,D,Since I was ten years old.这道题应该选D,但为啥其它的不行

现在完成时的答句用一段时间表示.一般比较常见的有since、for之类的.
关于这道题,这个解释就行了