Section A 内容详解 1.By the time I got outside, the bus had already left. a．当介词by 后接一个过去时间点的时候，by 介词短语表示的是“到过去这一时间点为止”或“在这一过去时间点之前”，强调在这一时间之前的情况或结果，因此主句谓语动词通常用过去完成时。如： We had planted about thirty thousand trees by last weekend. 到上周末为止我们已经植了大约三万棵树。 He had learned enough by himself to read newspaper in English by the age of fifteen. 到十五岁时他自学英语已达到了能读英语报纸的水平。 b．by now 意为“到现在为止”，在句中作状语。句子谓语动词通常用现在完成时。如： I have learned about 1800 English words by now. 到现在为止我已经学了大约 1800 个英语单词。 2.过去完成时的一般用法 过去完成时表示在过去某一时间或者动作以前已经发生或者完成的动作，或者从过去某一时间开始，持续到过去另一时间的动作、结果或者状态；或表示到过去某时为止已有的经历或经验。这个时态表示“过去的过去”，在句中一般有另一过去时间或动作与之比较。如： When I got to the bus stop, the bus had gone. 我到车站时，公共汽车已经开走了。（got 以前的动作） We had had breakfast when she came. 她来时，我们已吃过早饭了。（came 以前的动作） By the end of last term, we had learned more titan one thousand English words. 到上学期结束时，我们已经学了一千多个英语单词。（到上学期末为止的结果） The lain had stopped when I started out. 我出发时，雨已经停了。 She bad learned some English before she came to our school. 她来我们学校以前学过一些英语。（came 以前的情况） 3.When I got to school, I realized I had left my backpack at home. a．realize(或 realise)作“认识”“了解到”解，可接名词或从句作宾语。如： When I got home, I realized I had left my keys in the backpack. 我到家的时候，才想起来我把钥匙落在背包里了。 Does he realize his mistake yet？ 他认识到自己的错误了吗？ b．realize 作“实现”解。如： Finally he realized his hope of becoming an artist. 最后他实现了当...
