【正文】 esterday , we cleaned the classroom. Now , the classroom is clean because we have cleaned it. 用法 1 強(qiáng)調(diào) 過去發(fā)生的動(dòng)作 對(duì) 現(xiàn)在產(chǎn)生的 結(jié)果或影響 1. My father bought many books for me yesterday . Now , I have a lot to read because ________________________________ 2. I saw this film last week. Now, I know this film because I_____________________. 3. I did my homework yesterday. Now, I can give it to the teacher because I______________ my father has bought many books for me. have seen it before have done it. “仍然，還 ” 用在疑問句和否定句中，放在句末。 如不能說： He has borrowed the book for two months.(ⅹ ) 但可以說： He has kept the book for 2 months. 或： It has been 2 months since he borrowed the book. 或： Two months has passed since he borrowed the book. 這些瞬間動(dòng)詞常與它對(duì)應(yīng)的可以表示時(shí)間段的詞語進(jìn)行互換。 如： since 1997, since two years ago,since last week 。詞尾 為“元音字母 +y”時(shí)，直接加 d；如 : played stayed studied cried ④ 末尾只有一個(gè)輔音字母的重讀閉音節(jié)是，雙寫最后一個(gè)輔音字母加 ed. 如： stopped dropped 動(dòng)詞的過去分詞的規(guī)則變化 不規(guī)則動(dòng)詞的過去式以及過去分詞 巧記規(guī)律 AAA: put– put –put let—let –let ABA: bee—became—bee ABB: stand—stood—stood ABC: eat— ate—eaten AAA costcostcost readreadread putputput cutcutcut letletlet setsetset beatbeatbeat hithithit hurthurthurt spitspitspit ridridrid 一、原形、過去式和過去分詞的詞形和讀音都相同的單詞，結(jié)尾字母一般是 t或 d。 I have already read this book. 有時(shí)，也用在疑問句中表示驚訝。t seen much of him recently (lately). We have seen that film before. Have they found the missing child yet ？ 4. 現(xiàn)在完成時(shí)常常與表示頻度的時(shí)間狀語連用 ,如 often, sometimes, ever, never, twice, on several occasion等 : Have you ever been to Beijing？ I have never heard o