prefect全英解析.doc

present perfectThepresent perfectis formed from the present tense of the verbhaveand thepast participleof a verb:The present perfectcontinuousis formed withhave/has beenand the-ingform of the verb:UseWe use the present perfect tense: for something that started in thepastandcontinuesin thepresent:Theyve been marriedfor nearly fifty years.Shehas livedin Liverpoolall her life.Note:We normally use the present perfect continuous for this:Shehas been livingin Liverpool all her life.Its been rainingfor hours. for something we have doneseveral timesin thepastandcontinueto do:Ive playedthe guitar ever since I was a teenager.Hehas writtenthree books and he is working on another one.Ive been watchingthat programme every week.We often use a clause withsinceto showwhensomethingstartedin the past:Theyve been stayingwith ussince last week.Ihave workedheresince I left school.Ive been watchingthat programme every weeksince it started. when we are talking about ourexperience up to the present:Note: We often use the adverbeverto talk about experience up to the present:My last birthday was the worst day Ihave ever had.Note: and we use never for the negative form:Have youevermetGeorge?Yes, butIvenevermethis wife. for something that happened in the past but is important at the time of speaking:I cant get in the house. Ive lostmy keys.Teresa isnt at home. I thinkshe has goneshopping.Im tired out. Ive been workingall day.We use the present perfect ofbewhen someone hasgoneto a place andreturned:A: Wherehave you been?B: Ivejust been out to the supermarket.A:Have you ever been toSan Francisco?B: No, butIve beento Los Angeles.But when someonehas not returnedwe usehave/has gone:A: Where is Maria? I havent seen her for weeks.B:Shesgone toParis for a week.Shell be back tomorrow.We often use the present perfect withtime adverbialswhich refer to therecent past:just; only just; recently;Scientistshaverecentlydiscovereda new breed of monkey.Wehavejustgotback from our holidays.or adverbials whichinclude the present:ever(in questions);so far;until now;up to now;yet(in questions and negatives)Have youeverseena ghost?Where have you beenup to now?Have you finishedyour homeworkyet?No,so farIveonlydonemy history.WARNING:We donotuse the present perfect with anadverbialwhich refers topast timewhich isfinished:I have seen that filmyesterday.We have just bought a new carlast week.When we were childrenwe have been to California.But we can use it to refer to a time which isnotyetfinished:Have you seen Helentoday?We have bought a new carthis week.past perfectWe use the verbhadand thepast participlefor thepast perfect:Ihad finishedthe work.Shehad gone.The past perfectcontinuousis formed withhad beenand the-ingform of the verb:Ihad beenfinishingthe workShe had beengoing.The past perfect is used in the same way as the present perfect, but it refers to a time in the past, not the present.We use the past perfect tense: for something that started in the past and continued up to a given time in the past:When George died he and Annehad been marriedfor nearly fifty years.She didnt want to move. Shehad livedin Liverpool all her life.We normally use the past perfectcontinuousfor this:She didnt want to move. Shehad been livingin Liverpool all her life.Everything was wet. Ithad been rainingfor hours. for something we had doneseveral timesup to a point in the past andcontinuedto doafter that point:He was a wonderful guitarist. Hehad been playingever since he was a teenager.Hehad written threebooks and he was working on another one.Ihad been watchingthe programme every week, but I missed the last episode.We often use a clause withsinceto show when something started in the past:They had been staying with ussincethe previous week.I was sorry when the factory closed. I had worked theresinceI left school.I had been watching that programme every weeksinceit started, but I missed the last episode. when we are reportingour experience and includingup to the (then) present:My eighteenth birthday was the worst day I had ever had.I was pleased to meet George. I hadnt met him before, even though I had met his wife several times. for something that happened in the past but is important at the time of reporting:I couldnt get into the house.I had lostmy keys.Teresa wasnt at home.She had goneshopping.We use the past perfect to talk about the past inconditions,hypothesesandwishes:I would have helped himifhe had asked.It was very dangerous.What ifyou had gotlost?I wishI hadnt spentso much money last month.perfective aspectWe use thepresent perfectto show that something has continued up to the presentTheyve beenmarried for nearly fifty years.Shehas livedin Liverpool all her life. or is important in the present:Ive lostmy keys. I cant get into the house.Teresa isnt at home. I think shehas goneshopping.We use thepresent perfect continuousto show that something has been continuing up to the present:Its been rainingfor hours.Weve been waitinghere since six oclock this morning.We use thepast perfectto show that something continued up to a timein the past:When George died he and Annehad beenmarried for nearly fifty years. or was important at that timein the past:I couldnt get into the house. Ihad lostmy keys.Teresa wasnt at home. Shehad goneshopping.We use thepast perfect continuousto show that something had been continuing up to a time in the past or was important at that time in the past:Everything was wet. Ithad been rainingfor hours.He was a wonderful guitarist. Hehad been playingever since he was a teenager.We usewillwith the perfect to show that something will be complete at some timein the future:In a few years theywill have discovereda cure for the common cold.I can come out tonight. Ill have finishedmy homework by then.We usewouldwith the perfect to refer to something thatdid not happenin the past but would have happenedif the conditions had been right:Ifyou had asked