从 句.doc

从 句 名词性从句（主语从句、表语从句和宾语从句） 引导名词性从句的连接词为： 从属连词that, whether, if（if不能引导主语从句） 疑问代词who, what, which 疑问副词when, where, how, why 名词性从句有下列共同之处：使用的连接词相同；一律用陈述句的语序；一般不用逗号和句子其他成分隔开。 名词性从句应注意下列几点： 1、主语从句充当主语一般放在句首，但为了保持句子的平衡，大多数的主语从句可采用“It is + 名词（形容词或分词）+ 主语从句”形式。但是，当what引导的主语从句用来表示“…东西”的时候，则不能用it作形式主语结构。 e.g: When we shall have another debate is still a question. (It is still a question when we shall have another debate.) It is quite obvious that we need more equipment. What he needs is more practice. 2、当动词doubt用在肯定句时，其后的宾语从句连接词可用whether, if；当它用在否定句或疑问句时，其后的从句连接词只能用that。 e.g: I doubt whether/if he can come. I dont doubt that she can do the job well. 3、whether和if均可引导宾语从句，但whether可作介词后的宾语从句，还可与or…或or not连用。而if则只能引导动词后的宾语从句。 e.g: I wonder whether I will catch the last bus or not. He is always thinking of whether the job is suitable for him. I am wondering whether/if the letter is over-weight. 4、介词后一般不接that引导的宾语从句，只是在in, but, except等少数几 个介词后可构成固定搭配，即in that（在于…；因为），but that（要不是…），except that（除了…）。 e.g: The paper was perfect except that there were some misprints. 状语从句 A、时间状语从句 1、as soon as, the moment, the minute, the instant, once, directly, immediately等连词表示“一就”，主句和从句的时态相同。 e.g: The moment I saw him, he ran away. They told me the news immediately they got the message. 2、no sooner…than, hardly/scarcely…when也表示“一就”，但主句用过去完成时，从句用过去时。 e.g: Hardly had he gone to bed when the door bell rang. 3、while只表示持续性动作，不表示短暂性动作，主句和从句动作同时发生；as也可表示持续性动作，但时间持续较短，主句和从句动作同时发生；when既可表示持续性动作，又可表示短暂性动作。 e.g: While the boys were discussing the car accident, Ben put in that the road was icy. The volume varies ____ the temperature increases. a) before b) after c) during d) as (d) 4、till, until（主句为肯定式，谓语是延续性动词，意义为：“一直到…为止”；主句为否定式，谓语多为非延续性动词，意义为“直到…才”）。not until放在句首时，主句的主谓要倒装。 e.g: She stood there till/until he had passed out of sight. He didnt stop to rest until he had finished the work. (Not until he had finished the work did