一、 ＂there be＂结构
　　考生病句：
　　1. there are many people like to go to the movies.
　　2. there are different kinds of vegetables can be bought on the market by people.
　　正确表达：
　　1. there are many people who like to go to the movies.
　　2. there are different kinds of vegetables that people can buy on the market.
　　这两个例句的错误比较有普遍性，因为在历次考试中有不少考生不能正确运用there be这一最常用的句式。在这种结构中，there是引导词，没有实际意义。be在句中作谓语，有时态和数的变化。
例如：
　　1. there was no school in the village at that time. (=there was not a school...)
　　注意：在否定句中，否定词用no，也可用not a或not any。not a后接单数名词，not a 后接复数名词，no后面的名词单复数都可以。
　　2. there is not a moment to be lost.
　　3. there are many people rushing into the cities every year.
　　4. there are many things we can do to prevent traffic accidents.
　　5. there is no use holding back the wheel of history.
　　从以上例句还可看出，句中的主语后面可接多种修饰语，如介词短语、不定式短语、定语从句、分词短语等等。这无疑使该结构增加了表现力，使句子表达内容更加丰富。 在运用这一结构时，考生最容易犯的错误是在there be之后又用了一个动词作谓语，使句子结构出现严重错误。这里列举的考生的典型错误均属这种情况，对此我们在写作中要格外注意。

　　二、 比较结构
　　考生病句：
　　1. comparing with the bike, the car runs much faster.
　　2. the climate in walton is colder than other cities.
　　正确表达：
　　1. compared with the bike, the car runs much faster.
　　2. the climate in walton is colder than that of other cities.
　　评议与分析：许多考生在作文中用compare或than表示比较，但相当多的表达有误。
　　在例1中，对两个事物进行比较的句式为compared with a, b...,只能用compare的过去分词，不能用现在分词，因为b是分词的逻辑主语，只能被比较。在例2中，考生误将'天气'与'城市'进行比较，而二者没有可比性，只有将后者改为'其他城市的天气'才符合逻辑，很显然，考生的错误是受了汉语表达习惯的影响。
　　比较结构是常用结构，正确地使用这一结构可以使文章的句式增加变化，有利于提高写作成绩。一般说来，考生若能恰当、正确地运用这一结构，其写作成绩应在5分以上。
下面是比较结构的一些常用的表达方法。
　　1． 同级比较
　　1） in 1998 we produced as many cars as we did in the previous five years.
　　2） we have accomplished as much in the past three years as would have taken ten years
　　　　 in the past.
　　2． 比较级
　　1） children now enjoy better medical treatment than before.
　　2） we can live longer without food than we can (live ) without water.

　　3． 最高级
　　1） this is the most interesting book i've ever read.
　　2） of all his novels i like this one best.
　　4． the more…the more…结构
　　1) the harder you work, the greater progress you will make.
　　2) the more a man knows, the more he discovers his ignorance.
　　5． 选择比较
　　1) i prefer staying at home to going out.
　　2) they prefer to work rather than (to) sit idly.
　　3) he prefers to work alone.
　　注意：这里的1）句用的是prefer a to b结构，to为介词，后接名词或动名词；2）句是以不定式作　　　prefer的宾语；3）句用法同2），只是不把rather than部分表达出来。
　　6． 对比
　　1) motion is absolute while stagnation is relative.
　　2) he is tired out, whereas she is full of vigour.
　　注意：while 和whereas均可用于连接两个意义对立的分句，相当于汉语的'而'字。许多考生能较好地运用这一句式，尤其在图表作文中。
　　三、 表达原因的结构
考生病句：
　　1. the real reason to our failure is not far to seek.
　　2. the reason for this is because some people want to earn plenty of money without
　　　　 working hard.
正确表达：
　　1. the real reason for our failure is not far to seek.
　　2. the reason for this is that some people want to earn plenty of money without working
　　　　hard.
评议与分析：
　　以上两个病句分别引自92年1月和97年12月四级考试的考生作文。从遣词造句上看，这两位考生具有一定的写作能力，not far to seek, plenty of money以及without working hard等均运用正确、恰当。但令人遗憾的是，第一位考生不知道reason不与to搭配而应接介词for，第二位考生犯了一个中国学生常犯的错误，就是用because引起表语从句，because这个词不能引起表语从句，在本句中只能改用that才正确。
　　掌握好表达原因的结构是十分重要的，几乎所有的写作试题都要求写原因或可以写原因。在大学英语四、六级考试、研究生入学英语考试以及toefl考试中，写作的文体基本上是议论文，而议论文的基本模式是摆事实、讲道理，讲道理就是说明原因。写作测试的文体决定了表达原因结构的重要性。
　　英语中用来表达原因这一概念的结构有多种。我们可用as , because, since, seeing that, considering that, now that, not that...等词组引出表示原因的从句。例如：
　　1. now that we have seen these great achievements with our own eyes, we feel more
　　　　proud than ever of our country.
　　2. professor liu is strict with us because he wants us to make rapid progress.
　　3. since we live near the sea, we enjoy a healthy climate.
　　4. pollution is still a serious problem, not that we don't have the ability to solve it, but that
　　　　some people have not realized the consequences of the problem.
　　我们还可以借助某些词语用简单句表达原因结构。例如：
　　1. the reason for this change is quite obvious.
　　2. diligence is the key factor of success.
　　3. idleness is the root of all evils.
　　4. he was ashamed to have made the mistake.(=he was ashamed that he had made the
　　　　mistake. =he was ashamed because he had made the mistake.)
　　除了上述的例句外，英语中还有很多或易或难的表达原因的结构。我们在进行写作训练的时候，不能满足于一知半解，要讲究书面语言的正确性和准确性。比如，because是最常用的引导原因从句的连词，语气最强，表示直接的原因，若because置于句首，后面的主句不能再用so。用as引导的原因从句语气较弱，所说明的原因是附带的，而since表示的原因暗示着是稍加分析之后才能推断出来的原因。
　　四、 否定结构
　　考生病句
　　1. some people think we needn't to worry about fresh water.
　　2. nowadays many people don't like to go to the movies, too.
　　正确表达：
　　1. some people think we needn't worry (或don't need to worry) about fresh water.
　　2. nowadays many people don't like to go to the movies, either.
评议与分析：
　　例句1选自96年1月四级考生作文，例句2选自92年1月六级考生作文。例句1 的错误在于该考生混淆了need作为情态动词和作为普通动词的用法。need作为情态动词时，主要用于否定句，后面的动词不带to, needn't worry，作we的谓语。need作为实意动词时，可用于肯定句、否定句和疑问句，don't need to worry 中的to worry作don't need的宾语。例句2的错误在于该考生混淆了too和either的区别，这两个词都表示'也'的意思，但是在英语中too, also只能用于肯定句，而either只能用于否定句。