1.表示原因1）Therearethreereasonsforthis.2）Thereasonsforthisareasfollows.3）Thereasonforthisisobvious.4）Thereasonforthisisnotfartoseek.5）Thereasonforthisisthat...例如：Therearethreereasonsforthechangesthathavetakenplaceinourlife.Firstly,people’slivingstandardhasbeengreatlyimproved.Secondly,mostpeoplearewellpaid,andtheycanaffordwhattheyneedorlike.Lastbutnotleast,moreandmorepeopleprefertoenjoymodernlife.2.表示好处1）Ithasthefollowingadvantages.2）Itdoesusalotofgood.3）Itbenefitsusquitealot.4）Itisbeneficialtous.5）Itisofgreatbenefittous.例如：Booksarelikefriends.Theycanhelpusknowtheworldbetter,andtheycanopenourmindsandwidenourhorizons.Therefore,readingextensivelyisofgreatbenefittous.3.表示坏处1）Ithasmoredisadvantagesthanadvantages.2）Itdoesusmuchharm.3）Itisharmfultous.例如：However,everythingdividesintotwo.Televisioncanalsobeharmfultous.Itcandoharmtoourhealthandmakeuslazyifwespendtoomuchtimewatchingtelevi-sion.4.表示重要、必要、困难、方便、可能1）Itisimportant（necessary,difficult,convenient,possible）forsb.todosth.2）Wethinkitnecessarytodosth.3）Itplaysanimportantroleinourlife.例如：Computersarenowbeingusedeverywhere,whetherinthegovernment,inschoolsorinbusiness.Soon,computerswillbefoundineveryhome,too.WehavegoodreasontosaythatcomputersareplayinganincreasinglyimportantroleinourlifeandwehavesteppedintotheComputerAge.5.表示措施1）Weshouldtakesomeeffectivemeasures2）Weshouldtryourbesttoovercome（conquer）thedifficulties.3）Weshoulddoourutmostindoingsth.4）Weshouldsolvetheproblemsthatweareconfronted（faced）with.例如：Thehousingproblemthatweareconfrontedwithisbecomingmoreandmoreserious.Therefore,wemusttakesomeeffectivemeasurestosolveit.6.表示变化1）Somechangeshavetakenplaceinthepastfiveyears.2）Agreatchangewillcertainlybeproducedintheworld’scommunications.3）Thecomputerhasbroughtaboutmanychangesineducation.例如：Somechangeshavetakenplaceinpeople’sdietinthepastfiveyears.Themajorreasonsforthesechangesarenotfartoseek.Nowadays,moreandmorepeopleareswitc