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 vigor.
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：
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.