Unit 9 Lesson 1 To Clone or Not to Clone 完成时课件 2022-2023学年北师大版（2019）高中英语选择性必修第三册

UNIT 9 Human Biology Lesson 1 To Clone or Not to Clone 语法---完成时 The forms (形式)： present perfect 现在完成时 have / has done present perfect continuous 现在完成进行时 have / has been doing past perfect 过去完成时 had done past perfect continuous 过去完成进行时 had been doing 1现在完成时 l.形式：主语+have/has+done 2.用法： (1)表示动作发生在过去，到现在已完成，强 调对现在造成的影响或结果，常与yet, already, just, before, lately等词连用。 eg. I haven't finished reading the book yet,soI can't return it to the library. 我还没有把这本书 读完，因此不能把它还给图书馆。 (2)表示动作从过去某时开始一直持续到现 在，还有可能继续下去，常同these days, recently, so far, in the last/past…, "for+时间 段"和"since+时间点"等连用。 eg. In the past forty years this country has made great advances in science and technology.近四 十年来，该国在科学技术方面有了很大发展。 2. 现在完成进行时 1.形式：主语+have/has+been+doing 2.用法 (1)表示动作从过去某时开始，一直延续到说 话时刻，还在继续进行或可能进行下去，常与 表示一段时间的状语连用。 eg. We have been doing everything'possible to improve the working conditions.我们一直在尽 一切努力改善工作条件。 (2)表示一个动作从过去某时开始，一直延续 到说话时刻刚结束。 eg. I have just been waving goodbye to her . 我刚才一直都在向她