Since ancient times,people (send) ____________messages in many different ways.

题目

Since ancient times,people (send) ____________messages in many different ways.
为什么要用have sent不用have been sent...since不是用于现在完成时种么...

答案

have sent是主动
have been sent是被动
二者都是现在完成时态.
在这句话中people是主动send messages,并不是people被sent到什么地去了.
呵呵,这样的解释应该ok吧.