I couldn't have won the award without your assistance.

　　重点

　　couldn't have won意为“本来不会赢”，是虚拟语气的一种，表示对过去情况的假设。

　　考点归纳

　　“情态动词+现在完成时”句型的用法很多。如：

　　must have+done sth. 表示对过去可能发生的事情的推测，意为“肯定”。如：

　　Mary has gone to work, but her bicycle is still here. She must have gone by bus. 玛丽已经去上班了，但是她的自行车还在这儿。她一定是坐公共汽车去的。

　　would like to have done sth. 意为“本打算做某事”。如：

　　I would like to have read the article, but I was very busy then. 我本来想读一读那篇文章，但是当时太忙了。

　　needn't have done sth. 意为“本没必要做某事”。如：

　　I dressed very warmly for the trip, but I needn't have done so. The weather was hot. 为了旅行，我穿得很暖和，但是其实没有必要穿这么多。天气比较热。

　　ought to/should have done sth. 表示“本应该做某事，而事实上并没有做”。否定句表示“不该做某事而做了”。如：

　　1) You ought to have been more careful in this experiment. 在做这个试验的时候，你本应该更细心一些。

　　2) He ought not to have thrown the old clothes away. 他本不该把那些旧衣服扔了。