词汇与语法题做多了往往就能达到这样的境界:有些题目只要看一眼(两秒左右)就知道正确选项,根本没有必要看完或看懂全句。可是我们也常常发现,本来只需数秒就能解决的题目,个别学生还是翻来覆去地看,甚至会选错。如:

　　1. All flights ________ because of the snowstorm, we decided to take the train instead.

　　A. were canceled

　　B. had been canceled

　　C. having canceled

　　D. having been canceled

　　2. Weather ________, the picnic will be held as scheduled.

　　A. permits B. permitting

　　C. will permit D should permit

　　正确的解题思路是:1. 逗号后 (Part 2) 为一个独立的分句,逗号前只可能是个从句或短语;2. Part 1前没有从属连词就排除了该部分为从句的可能性, 因此句1可排除A、B,句2可排除A、C、D;3. 航班被取消,句1的Part 1只能用被动,正确选项为D

　　在被问及为什么选错或花那么长时间做类似题目时很多学生说不知道"逗号后为一个独立的分句时逗号前只能是一个从句或短语、分句间必须有并列连词或从属连词"。由此看来,解这类题的关键是掌握英语的基本句子结构。

　　从结构上看,英语句子可分为三类:简单句、并列句、复合句。

　　一、简单句:只有一个主谓结构而且句子的各个成分均用单词或短语表示。需要强调的是,"一个主谓结构"是指只有一个主语部分和一个谓语部分,主语部分可以有一个或多个并列的主语,谓语部分可以有一个或多个并列谓语。例:

　　Poor health and lack of money may both be barriers to educational progress.(并列主语)

　　We will always unite, fight and win victories together. (并列谓语)

　　二、并列句:两个或多个相互独立的主谓结构用并列连词串联起来就成为并列句。例:

　　We love peace but we are not afraid of war.

　　Modesty helps one to go forward, whereas conceit makes one lag behind.

　　We must double our efforts, or we'll never be able to catch up with the others.

　　比较:1. He lives in the country and goes to work by car.

　　2. He lives in the country and he goes to work by car.

　　句1为简单句,有一个主语和两个并列谓语。句2为并列句,拿掉连词 and前后两部分仍然独立存在。

　　三、复合句:由主句和从句组成的句子叫复合句。复合句中至少要有一个主句,从句的数量则没有限制。例:

　　Animals that hibernate practice energy conservation to a greater degree than deer do.

　　划线部分为主句,that hibernate为定语从句,than deer do为比较状语从句。

　　另外,在英语长句中我们经常看到由并列句和复合句组合起来的句子,有些语法学家将之称作并列复合句。并列复合句的结构是:几个并列的分句中至少有一个是复合句。例:

　　a. Energy is the currency of the ecological system and life becomes possible only when food is converted into energy, which in turn is used to seek more food to grow, to reproduce and to survive.

　　划线的and连接两个并列的分句。分句2由主句life becomes possible和时间从句only when food is converted into energy 组成。另外,在分句2中which 引导的定语从句修饰先行词energy。

　　b. Somewhere or other—I think it is in the preface to Saint Joan—Bernard Shaw remarks that we are more gullible and superstitious today than we were in the Middle Ages, and as an example of modern credulity he cites the widespread belief that the earth is round.

　　划线的and连接两个并列的分句。 另外,这两个分句都是主从复合句:前者由主句Bernard Shaw remarks和that引导的宾语从句组成, 而宾语从句又是由主句we are more gullible and superstitious today和比较状语从句than we were in the Middle Ages组成。后者由主句he cites the widespread belief和同位语从句that the earth is round组成。

　　根据以上分析可以看出:在一个英语句子中,分句与分句、主句与从句、从句与从句之间都必须用并列连词或从属连词连接。但下列句子不遵守这一规则:

　　1. 两个关系密切的句子间 (常见的为因果关系,通常用逗号或分号隔开):

　　Hurry up, it's getting late.

　　It was getting dark; she must go back.

　　2. 插入语 句子中间插入或末尾加上一句话表示征求对方的意见(a)或表明自己的看法(b):

　　(a) What do you think I should do?

　　That's a better solution, don't you think?

　　(b) This, I think, was mainly due to our lack of experience.

　　3. 其它独立成分

　　We are firm on this point, we are! (表示强调)

　　"You are welcome," the girl said. (表明直接引语的出处)

　　4. 反意问句

　　You have nothing against it, have you?

　　Have a little more coffee, will you?

　　句子分析是学习英语的一个重要手段,它能使我们正确理解句子,使自己应用语言时不至于犯结构上的错误。然而,语言是不断变化的,正式文本中被认为是错误的东西放在非正式文本中则是可行的,今天被认为不符合语法规则的东西说不定将来就会被认可。句子分析是必要的,但要适可而止,因为没有必要进行过细的分析,有时甚至做不到。只要能掌握句子的主要结构并能正确理解就行,不必根据几个句型对所有句子进行分类。

　　(文/臧玉秋　英语辅导报大学教师版04~05学年第9、10期;版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)