have been they have been doctors中been后直接加名词doctors.那为什么have been to China中必须加to等介词才能加名词China?

Where have they been? They have a____ been there they have been there before.so have i they have been there before.(),() 改为同义句 what have they been doing 是什么时态 What places have they been?怎么翻译? where have they been?是现在完成时吗? they have been in kate's for they have been the subject of debate they have been acting up more lately They have been here once.把been换成came怎么样 They have never been opened.为什么不可以是They never have been opened. they have been here since 1988,对1988进行提问,（）（）have they been here? They have been friends for 6 years. 改为同义句 They have been friends _______ _______. They have been skating for five hours 同义句 They have been skating_______ _____ ________ ______ Where have they been?能不能说：They have been in their room. have been have been have been