一、混淆定语从句与并列句 请看下面两题：http://yingyu.chazidian.com (1) He has two children, and both of _____ are abroad. A. them B. which C. whom D. who (2) He has two children, both of _____ are abroad. A. them B. which C. whom D. who 【分析】第(1)题选A，第(2)题选C。由于第(1)题中用了并列连词and，从而使整个句子为并列句，and后应是一个独立的简单句，所以选A不选C；第(2)题没有并列连词and，both of whom are abroad为非限制性定语从句。
二、混淆定语从句与表语(从句) 请看下面的试题： (1) Your coat is still _____ you left it. A. where B. there C. there where D. the place where 【分析】答案选A，where引导的是表语从句(=在…的地方)，而不是定语从句。 (2) Is this school _____ your father worked in ten years ago? A. where B. what C. that D. the one 【分析】答案选D，this school为句子主语，the one 为表语，your father worked in…为定语从句。不要误认为this是句子主语，否则school前应加冠词the。比较： Is this the school _____ your father worked in ten years ago? A. where B. what C. that D. the one (选C) Is this the school _____ your father worked ten years ago? A. where B. what C. that D. the one (选A)
三、混淆定语从句与状语从句 请看下面的试题： (1) I went upstairs ______I heard some crying. A. where B. when C. that D. which 【分析】答案是B而不是A，when的意思是“当…的时候”，引导的是时间状语从句。(upstairs为副词，不宜用作先行词) (2) He is _____ a clever boy _____ we all like. A. such, that B. such, as C. so, that D. so, as 【分析】答案应选B，而不是A。such … that …(如此…以致…)用于引导结果状语从句，其中的that不充当句子成分，而such…as…中的as为关系代词，用以引导定语从句并在定语从句充当句子成分。上句中第二空之所以选as，是因为它用作动词like宾语。
四、误加与关系代词同义的人称代词 误：He is a man everyone respects him. 正：He is a man everyone respects. 他是一个人人都敬重的人。
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五、混淆关系代词与关系副词 有的同学一看到先行词是表示时间、地点、原因的名词，就认为一定要用关系副词，其实也一定。在此情况下，还要看关系词在定语从句中是用作什么成分，若是用作状语，则用关系副词，若不是用作状语(如用作主语、宾语等)则不能用关系副词，而用关系代词。比较： This is the factory where I want to work. 这就是我想工作的工厂。(work为不及物动词where在从句中用作状语) This is the factory that I want to visit. 这就是我想参观的工厂。(visit为及物动词，that用作visit的宾语) The reason why he can’t come is that he is ill. 他没来的是因为他病了。(come为不及物动词，why在定语从句中用作状语) The reason that he put forth is very important. 他提出的理由很重要。(put forth为及物动词，that在定语从句中用作其宾语)
六、因逗号误判which 有的同学一看见逗号，就以为一定要选which而不选that，但问题是有时根本就不是定语从句： (1) If a book is in English, _____ means slow progress for you. A. as B. which C. what D. that (2) When I say two hours, _____ includes time for eating. (D19/541) A. as B. which C. what D. that 【分析】以上两题均应选that，而不能选which，因为它们根本不是定语从句。之所以选that，是因为句中已有if和when引导的状语从句，逗号后为主句，that为主句主语。
七、混淆which与whose 两者在定语从句中都可用作定语，区别是：whose 的意思相当于 one’s，而 which 的意思则相当于 that 或 this。比较： (1) This is Mary, whose [= and her] father we met last week. (2) Call again at 11, by which time [= and by that time] the meeting should be over.