Unit1TalesoftheunexplainedGrammarandusagePresentperfecttenseGrammarandusagePresentperfecttense1.PoliceinAmericahavesteppeduptheirsearchforafifteen-year-oldboywhowentmissing…2.Thisincidenthasreceivedgreatinterestduetoreportsof…3.Ihaven’tseenJustinsince.Gooverthenewsstory,Boymissing,policepuzzled,andfindthesentencesusingthepresentperfecttense.4.It’shappenedtome!5.Whenasked…,whohastakenchargeofthecase,told…6.So,whilewehavenotdismissedtheidea,wearelookingintootherpossibilitiesaswell.现在完成时现在完成时用来表示之前已发生或完成的动作或状态，其结果的确和现在有联系。动作或状态发生在过去但它的影响现在还存在；也可表示持续到现在的动作或状态。其构成：have(has)+过去分词Johnhasbrokenhisleftleg.1.WehavestudiedEnglishforaboutfiveyears.2.Theyhavelivedinthesouthsincetheirdaughterwasborn.3.Ihavereadyourarticlethreetimes.It’swellwritten.4.Thestudenthasfinishedherhomeworkalready.5.Erichasgonebacktohishometowntoday.Moreexamples现在完成时的用法：1）表示过去发生或已经完成的某一动作对现在造成的影响或结果。通常与表示包括现在在内的时间副词just，already,before,yet,never,ever等状语连用。例如：Ihaveneverheardofthatbefore.Haveyoueverriddenahorse?Shehasalreadyfinishedthework.I’vejustlostmysciencebook.2）表示过去已经开始，持续到现在,也许还会持续下去的动作或状态。可以和表示从过去某一时刻延续到现在的一段时间的状语连用。如：for和since，以及sofar,now,today,thisweek(month,year)等。Ihaven’tseenherthesedays.ShehaslearntEnglishfor3years.Theyhavelivedheresince1990.WhathashappenedtotheUSAinthelast350years?注意：表示短暂时间动作的词，如come,go,die,marry,buy等的完成时不能与for,since等表示一段时间的短语连用。3）现在完成时还可以用在时间和条件状语从句中,表示将来某时完成的动作。例如：I’llgotoyourhomewhenIhavefinishedmyhomework.Ifithasstoppedsnowinginthemorning,we’llgotothepark.4）havebeen(to)和havegone(to)的区别：have/hasbeen(to)表示“曾经去过”某地，说话时此人很可能不在那里，已经回来。侧重指经历。have/hasgone(to)表示某人“已经去了”某地，说话时此人在那里，或可能在路上，反正不在这里。HehasbeentoBeijing.(人已回来,可能在这儿)HehasgonetoBeijing.(人已走,不在这儿)用于现在完成时的句型Itisthefirst/secondtimethat…在这个结构中的从句部分，用现在完成时。如：ItisthefirsttimethatIhavevisitedthecity.ThisisthefirsttimeI’veheardhimsing.Thisis+形容词最高级+that…在这种结构中，that从句要用现在完成时。如：ThisisthebestfilmthatI’veeverseen.一般过去时与现在完成时的区别一般过去时表示过去某个时间发生的动作，与具体的过去时间状语连用。现在完成时强调对现在的影响，不与具体过去时间状语连用，但可与ever,never,before,just,already连用。Ifinishedmyhomeworkanhourago.Ihavealreadyfinishedmyhomework.Isawthisfilmyesterday.（强调看的动作发生在过去某个时间）Ihaveseenthisfilm.（强调对现在的影响，即电影的内容已经知道了）Whydidyougetupsoearly?（强调起床的动作已经发生过）Whohasn’thandedinhispaper?（有人卷子未交，强调结果）1.—Ididn’taskforthenamelist.Why______onmydesk?—Iputitherejustnowincaseyouneededit.（2011安徽）A.doesitlandB.hasitlandedC.willitlandD.haditlandedB高考链接2.Uptonow,theprogram____thousandsofchildrenwhowouldotherwisehavedied.(2010山东)A.wouldsaveB.savesC.hadsavedD.hassaved3.Whenyouarehome,giveacalltoletmeknowyou______safely.(2010全国I)A.arearrivingB.havearrivedC.hadarrivedD.willarriveDB【2012江西卷】--Look!Somebody____thesofa.--Well,itwasn’tme.Ididn’tdoit.A．iscleaningB．wascleaningC．hascleanedD．hadcleaned答案：C解析：句意...
