It-is-+adj.-+动词不定式的用法

Itis+adj.+动词不定式的用法------------------------------------------I.Itis+adj.+todosomething结构句中it是形式主语，真正主语是动词不定式todosomething。因此也可以表达为todosomething+is+adj.。e.g.Itisamazingtodrivepastfieldswhichseemtogoonforeverorwholehillscoveredwithneatrowsofgrapevines。本句形式主语为it。真正主语todrive…grapevines移到了句子后部，使句子变得平稳，不致主语太长。如果把真正主语放在前面，那么整个句子就显得头重脚轻。因此，就用it作为先行主语。这种结构还有两种动词不定复合结构。1.Itis+adj.+forsomebodytodosomethinge.g.Itwasverydifficultforthemtoflybecausemenhavenotgotwings.此句真正的主语是动词不定复合结构forthemtofly。其中them是tofly的逻辑主语。2.Itis+adj.+ofsomebodytodosomethinge.g.Itissensible_____youtobringanumbrellainsuchweather.A.inB.forC.withD.of答案为D。这里sensible跟逻辑主语you的关系是表达人的特点、性格、本质等。像此类形容词还有kind,foolish,clever,wise,friendly等。II.Itis+名词+todosomething结构e.g.Itisgreatfuntoseethepandaswalkinginthezoo.III.另外,it作先行主语时还有其他用法1.it+及物动词+宾语+不定式e.g.Itcostme100dollarstorepairthecar.Ittakesmetwohourstofinishmyhomeworkeveryday.Itgavemegreatpleasuretowatchthem.2.it+be+名词/形容词+doinge.g.Itisnousestudyingforanexamatthelastminute.Itisawasteoftimetalkingtohim.Itispleasantsittinghere.ExerciseI.Choice1.Todayitiseasy_______on-lineandmillionsofpeopleusetheInterneteveryday.A.getB.togetC.getsD.got2.Itisclever_______youtoanswersuchaquestion.A.forB.onC.withD.of3.______funitistorideonacamelinthedesert!A.WhatB.WhataC.HowD.Howa4.Ittakes3daysfortheparcel_______AmericabyairmailfromShanghai.A.reachB.reachedC.toreachD.reaches5.______importantthingitistodoeyeexerciseseveryday!A.WhatB.WhataC.WhatanD.How6.Itisnouse_______abouttheschoollunch.A.complainB.complainingC.tocomplainD.complainedII.用it作形式主语改写句子1.TospeakEnglishmoreisveryimportantforyou.2.Todomoreexercisesisveryhelpful.3.Todoismoreimportantthantosay.4.Tohelpothersisourduty.5.TogototheSouthPoleistheboy'swish.6.Todrinkplentyofwaterisgood.Key:I.1.B2.D3.A4.C5.C6.B