1、目的从句如目的所指的人与主句中的主语不同,或原主语再次被提到 ,则必须使用目的从句：Ships carry lifeboats so that the crew can escape if the ship sinks.大船上带有救生艇，万一船下沉船员可以逃生。This knife has a cork handle so that it will float if it falls overboard.这把刀的柄是用软木做的中，万一从船上掉下去，它可以浮在水面上。1. 目的从句常由 so that + will/would 或 can/could + 动词原形结构来表示。这里 can/cou
2、ld 意为 will/would be able to:They make $10 notes a different size from $5 notes so that blind people can (-will be able to) tell the difference between them.他们把十美元的纸币和五美元的纸币做成不同大小，以便使盲人可以区分开来。They wrote the notices in several languages so that foreign tourists could(=would be able to) understand them
3、.他们把通知用几国文字写出来，以便让各国游客都能看得懂。如句子的主要动词是一般现在时、一般完成时或一般将来时，则都可用can 和 will。如主要动词是一般过去时，则使用 could 和 would。I light/am lighting/have lit/will light the fire so that the house will be warm when they return.我点着/正在点着/ 已点着/ 将要点着炉子，以便等他们回来时屋子就暖和了。I have given/will give him a key so that he can get into the house
4、 whenever he likes.我已经给/会给他一把钥匙，好让他能随时进来。I pinned the note to his pillow so that he would be sure to see it.我把纸条用针别在他的枕头上，好让他一定能看得见。百合There were telephone points every kilometer so that drivers whose cars had broken down would be able to /could summon help.每公里都有求援电话点，以便汽车出了毛病时司机可随时呼唤帮助。2. so that/in
5、 order that/that +may/might 或 shall/should + 不定式结构也中构成目的从句。这种结构仅比 1 中所示的结构更为正规，在意思上是相同的。注意：so that 之后可跟 will/can/may/shall 或它们的过去式。论文检测In order that 或 that 之后只限跟 may/shall 或它们的过去式。That 除在戏剧、诗歌及文章中外极少单独使用。关于时态一致的规定与上文所述相同。下文的句子是很正式的：We carved their names on the stone so that/in order that future gene
6、rations should/might know what they had done.我们把他们的名字刻在石头上，为的是让后代们知道他们的事迹。These men risk their lives so that/in order that we may live more safely.这些人甘冒生命危险，为的是让我们生活更安全。3. 表示否定目的的从句由助动词（will/would 或 should）变为否定式构成：He wrote his diary in code so that his wife wouldnt be able to read it.为了不让妻子看懂，他用密码写日
7、记。He changed his name so that his new friends wouldnt/shouldnt know that he had once been accused of murder.为了不让新朋友知道他曾被指控犯有谋杀罪，他改了名字。Criminals usually telephone from public telephone boxes so that the police wont be able to trace the call.罪犯常在公用电话亭打电话，好让警察追查不到电话是从哪儿打来的。表示否定目的的从句常可用 to prevent + 名词/
8、 代词 + 动名词或 to avoid + 动名词来代替：He dyed his beard so that we shouldnt recognize him/to prevent us recognizing him/to avoid being recognized.他染了胡子，好让我们认不出/为了阻止/为了避免我们认出他。 （被动语态动名词）She always shopped in another village so that she wouldnt meet her own neighbours/to avoid meeting her own neighbours.她经常去另外一个村子购买东西，以免碰到她的邻居/为了避免碰到她的邻居。
