can和be-able-to的区别

和用法的区别Presentedby***它们用法上的不同主要体现在以下几方面:1.can只有两种时态,即can和could;而beableto有多种时态,如was/wereableto,will/shallbeableto,have/hasbeenableto等。e.g.I’llbeabletodrivethecarinaweek.Throughhisdiligentwork,thedeaf-mutehasbeenabletoreadandwriteinasignlanguage.2.表示过去通过努力终于做成了某事要用beableto，而不能用can。can和beableto都可以表示能力.can泛指一般的能力,beableto则主要指具体做到了某件事的能力.Icanswim.Iamabletoswim.(√)(√)Allthepeoplecouldescapefromthebigfireintime.Allthepeoplewereabletoescapefromthefireintime.(×)(√)3.can能表猜测，beableto不能。can的这种用法主要用于疑问句和否定句。其肯定形式是mustbe。e.g.•Somebodyisknockingatthedoor.Whocanitbe?•Itcan’tbeourteacherwhoisknockingatthedoor.•Itmustbeourteacherwhoisknockingatthedoor.4．can可以表“允许”,与may可以互换,此时不能用beableto代替。如：“Can/MayIsithere？”由于maynot有两个意思,即“不可能”和“不许可”,在口语中，表达这两种不同的含义是通过句重音来解决的。Hemaynotgohomethisweekend.Hemay`notgohomethisweekend.(Idon’tpermithimtogohomethisweekend.)He`maynotgohomethisweekend.(Hewillprobablynotgohomethisweekend.)而在书面表达时不可能使用句重音的手段,所以最好用can’t代替maynot来表示“不可能”：Hecan’tgohomethisweekend.5.can是情态动词，只能用作谓语成分，beableto是普通动词短语，既可以作谓语，也可以作非谓语。BeingabletospeakEnglishfluently,hehasnodifficultyincommunicatingwiththeAmericansattheparty.HowIlongtobeabletocommunicatewiththeforeignersinfluentEnglish!