请教英语高手:请帮忙解答几道题目,谢谢!1.ThebuscameafterI()forabouthalfanhour.A.havewaitedB.hadbeenwaiting2.You()thedaybeforeyesterdayifyoureallythoughtthiswasveryimportant.A.oughttocomeB.ought

　　请教英语高手:请帮忙解答几道题目,谢谢!

　　1.ThebuscameafterI()forabouthalfanhour.

　　A.havewaitedB.hadbeenwaiting

　　2.You()thedaybeforeyesterdayifyoureallythoughtthiswasveryimportant.

　　A.oughttocomeB.oughttohavecome

　　3.()formspace,ourearth,70percentofitssurfacecoveredwithwater,lookslikeablueplanet.

　　A.seenB.seeing

　　请说明理由,谢谢!

　　第1题用过去完成时,即A为什么不对?

　　第3题参考答案是选A,为什么?