1.Don't take his remarks so seriously.He is so upset that I

1.Don't take his remarks so seriously.He is so upset that I don't think he really knows what____A he said B.he'd said c.he's saying d.he says但是为什么不能用D?2.Roman Empire _______ for centuries.A.has existed B.existed C.had existed D.was existing但是for+一段时间为什么不是用完成时?3."What's wrong with your coat?""Just now when I wanted to got off the bud the man next to me ___on it."A.sat B.was sitting C.had been sitting D.had sat但是如果是要强调一直坐在他的外套上为什么不能用过去进行时?4.Great efforts to increase wheat production must be made if bread shortage___avoided.A will be B can be C.were to be D.is to be为什么?