Question

Have you ever been to London 为什么加been

Answer 1

一般是区别have been to 和have gone to。
前者是表示去过某地已经回来，比如-Where did you go during this holiday? -I have been to Beijing.
后者则表示去过还没回来，比如-Where is your Dad? -He has gone to Beijing.

追问

谢谢

追答

不客气

Answer 2

嗯，不知道

Answer 3

现在问你，以前去过伦敦没有，就用：have you ...
上周或者去年问你，上上周或前年以前去过伦敦没有，就用：had you ...
另外，在有些句型转换中也会遇到，比如：
she said, "have you ..." 改为：she said that had you ...