How long have you been collecting shells?与How long have you collected shells?的区别

题目

How long have you been collecting shells?与How long have you collected shells?的区别
还要介绍一下现在将来时!

答案

How long have you collected ...这是现在完成时,强调这件事现在已经完成了,问已经收集贝壳收集了多久,暗示接下来不收集了,或不收集的可能性很大.How long have you been collecting ...表示收集贝壳的事,从过去收集...