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.
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.)