先看这样一道中考题:(2010,达州市)When we got to Yushu airport,we were told that they____ more than 500 people from the ruins(废墟)by earthquake.A.has saved B.savedC.had saved D.have saved根据句意我们可以看出,他们"救人"这个动作发生在我们"到达"之前,"到达"是过去的动作,那么"救人"就成了"过去的过去",所以要用过去完成时,故正确答案为C。