新世纪高等院校英语专业综合教程第3册(综合英语3)第二单元答案第二部分Ex.Key--unit2-2.doc

Grammar Present perfect The present perfect simple tense an action that is still going on or that has stopped recently, but still has an influence on the present. It puts emphasis on the result. Use of present perfect putting emphasis on the result Example: She has written five letters. the action that is still going on Example: School has not started yet. the action that has stopped recently Example: She has cooked dinner. the finished action that has an influence on the present Example: I have lost my key. the action that has taken place once, never or several times before the moment of speaking Example: I have never been to Australia. Present Perfect Progressive The present perfect progressive expresses an action that has recently stopped or is still going on. It puts emphasis on the duration or course of the action. Use of present perfect progressive putting emphasis on the duration or course of an action (not the result) Example: She has been writing for two hours. the action that has recently stopped or is still going on Exam ple: I have been living here since 2001. the finished action that has an influence on the present Example: I have been working all afternoon. More examples: We have been studying English for 7 years. 我已经学了七年的英语。（现在仍然在学） He has been reading since this morning. 从今早起，他一直在看书。（现在还在看） We have been waiting for him all afternoon. 我们已经等了他整个下午。（现在还在等） 比较下列句子： He has been reading the book. 他一直在看书。（即便没有时间也能表示持续） He has read the book for an hour. 他已经看了1个小时的书。（需要时间） He has read the book. 他看过书了。（已经看过） NoteS: 1) The present perfect progressive focuses on the course of the activity or event which may or may not be finished. The present perfect focuses on the result of the activity or event, or just the fact that something has been achieved. Either the present perfect progressive or the present perfect is used to talk about activities or events that are repeated again and again until now. (p28 Exercise I: 1) If we use the present perf