By the time you arrive in London,we _____ in Europe for two weeks.填have been还是will have been

问题描述:

By the time you arrive in London,we _____ in Europe for two weeks.填have been还是will have been

后一个,因为句子的意思很明显是说你还没到伦敦,那等你到伦敦的时候,我们将已经在欧洲待了2周了.
这是一个将来完成时,我说的是还没实现的事,就不能用现在完成时