Unit9 Human Biology 语法知识点扫盲-2022-2023学年高二英语练好基础（北师大版2019选择性必修三）

Unit9 Human Biology 语法知识点扫盲 完成时态 观察句子 I am Li Fan, Chairman of the Students' Union. I am writing to draw your attention to some improper behaviour on our campus: littering and scribbling. It ①has been making our school dirty and unpleasant. It is clearly not appropriate for a student to litter and scribble about. Last week, the Students' Union held a meeting to seek some solutions to these problems. After the meeting，the headmaster said that the school ②had made efforts to improve this situation and more dustbins would be placed around. Recently, the Students' Union ③has set up specific rules against such behaviour. At the same time, all of us should develop good habits and better behave ourselves. We believe that with the joint efforts, our school will become a more enjoyable place in the near future. 感悟： 1．现在完成时强调动作的完成，如加黑处③；其结构为have/has＋现在分词。 2．现在完成进行时的构成：have/has been＋现在分词。现在完成进行时表示动作开始于过去，并一直持续到现在，动作可能仍在进行，也可能刚刚结束。如加黑处①。 3．过去完成时用于主从复合句，主从句动作都发生在过去，且有先后关系，如加黑处②。 语法知识精讲 完成时表示一个完成的动作，用来表示现在、过去或者未来某个时间点已经或者将会完成的动作。完成时包括现在完成时、现在完成进行时、过去完成时和过去完成进行时四种时态。 一、现在完成时 1．现在完成时的构成为have/has＋done，表示发生在过去的动作或存在的状态到说话时刚刚完成或结束。现在完成时常与up to now、so far、already、yet、now、recently、in the past few years、just等表示时间的短语连用。 2．在条件、时间或让步状语从句中，表示将来某时之前已完成的动作。 3．下列情况下常用现在完成时： ①It is/has been＋一段时间＋since从句 ②This/That/It is the first/second/...time that＋现在完成时 ③It/This is the best/worst/most interesting/...＋名词＋从句(现在完成时) ◆In the past few years，great changes have taken place in my hometown. 在过去的几年里，我的家乡发生了巨大变化。 ◆When you have learned English，you will find it a bridge to so much knowledge. 当你学习英语之后，你会发现它是通往丰富知识的桥梁。 ◆It is/has been twenty years since I saw her. 我已经二十年没见她了。 ◆This is the first time that we have seen a film in the cinema as a family. 这是我们全家第一次在电影院看电影。 ◆This is the most interesting novel he has ever written. 这是他写的最有趣的一部小说。 二、现在完成进行时 1．现在完成进行时的构成为have/has＋been＋doing，表示过去的动作持续到现在并有可能延续下去，常和for、since引导的时间状语连用。 2．表示重复性动作。 3．表示某种感情色彩。 ◆The manager has been telling the workers how to improve the