考研英语语法重难点精解不定式

考研英语语法重难点精解不定式
考研英语语法重难点精解不定式
动词不定式是一种非谓语动词，在句中不能单独作谓语。

一、不定式的时态(Tense)
以动词do为例：
语态时态主动被动一般式 to do to be done 完成式 to have done to have been done 进行式 to be doing 在上述表格中：（1）不定式的一般式表示的动作与谓语动词表示的动作或状态同时发生，前后紧接发生或在谓语动词的动作或状态之后。

例句： Nobody saw him to come into the office， for three of us were all busy with our own affairs.（saw和came into两动作同时发生）
分析：该句是复合句。

从句用for引导表原因。

译文：没有人看见他走进办公室，因为我们三个人都在各自忙碌着自己的琐事。

例句： The Smiths have invited me to go to their family party next Sunday， but I am afraid that I will be busy by then.（to go to...明显在谓语动词have invited之后）
分析：该句是并列句。

译文：斯密斯一家人已经邀请我下周日参加他们的家庭聚会，但是我担心到时脱不开身。

（2）不定式的完成式表示的动作发生在谓语动词表示的动作之前，可以用下述句型加以说明，在句型It is said/believed/reported/thought/that sth. /sb....中，可以用不定式的完成式来相互转换，即sb. /sth. is said/believed/reported/thought to be/to be done/to have done/to have been done。

例句： The local health organization is reported to have been
set up twenty?five years ago when Dr. Audon became its first president.(to have been set up发生在be reported 之前) 分析：该句是复合句。

when Dr. Audon became its first president是修饰twenty?five years ago的定语从句。

译文：据报道，这个地方卫生组织25年前就成立了，那时Audon博士就担任了首任主席。

例句： The Bunsen bumer is so named because it is thought to have been invented by Robert Bunsen， who was German by birth.（to have been invented发生在be thought之前）分析：该句是复合句。

because引导一原因状语从句，定语从句who was German by birth 修饰Robert Bunsen。

译文：本生灯的得名是因为人们认为它是由罗伯特·本生发明的，罗伯特·本生生于德国。

（3）不定式进行式表示动作正在进行，与谓语动词的.动作同时发生。

例句： They are said to be building another bridge across the river in that country. (to be building所表示动作与are said同时发生）
分析：该句是简单句。

译文：据说，他们正在那个国家架设另一座大桥。

二、不定式的用法
（一）充当主语
例句： It is naive to expect that any society can resolve all the social problems it is faced with once for all. （2001年第16题）分析：该句是复合句。

it是形式主语，真正的主语是to expect that any society...，it is faced with是修饰problems的定语从句，其前省略了作宾语的关系词。

译文：期盼任何一个社会能够一劳永逸地解决它所面临的各种社会问题的想法太天真了。

例句： It would be a shame to raise prices too much because
it would drive away the young people who are Stratford’s most attractive clientele.（选自2006年Text 2）
分析：该句是复合句。

其中it是形式主语，真正主语为to raise prices too much，because 后引导一状语从句，定语从句who are Stratford’s most attractive clientele修饰people。

译文：把票价抬得太高是不合理的，因为这会赶跑斯特福特镇最能吸引住的客源——年轻人。

大学网考研频道。