现在完成进行时的被动语态结构是have been +过去分词还是have been+doing例如：They have been collecting some stamps since2000Some stamps have been collected by them since 2000
问题描述：
现在完成进行时的被动语态结构是have been +过去分词还是have been+doing
例如：They have been collecting some stamps since2000
Some stamps have been collected by them since 2000
答