考生病句：

1. As is known to all of us that science and technology play an important role in the development of society.

2. It is known to us, practice makes perfect.

正确表达：

1. It is known to all of us that science and technology play an important role in the development of society. (或：As is known to all of us, science...)

2. It is known to us that practice makes perfect. (或：As is known to us, practice.。。)

评议与分析：

例句1是93年12月六级考试11分作文的评分样卷句子，例句2选自97年1月四级考试作文。很显然，两个考生混淆了it和as的用法。如果用it作形式主语，后面的主语从句必须由that引起;如果用as，则后面不能用that，因为as是关系代词，代表practice makes perfect。

It 在英语中是个相当活跃的代词，在写作中我们常要使用它。以下几种用法应熟练掌握，并能灵活运用。

1.作形式主语

It is necessary for us to master a foreign language skillfully. It makes difference whether we could purify the air or not.

2.作形式宾语

We find it rather difficult to prevent people from doing that. Modern science has made it possible for babies to grow healthily and for people to live longer.

3.引导强调句

It is only by this way that we can achieve success. It was then that people began to realize the importance of controlling population.

从语法结构来看，上述的句子都不难，或者可以说是考生相当熟悉的。然而在写作考试中，多数考生缺乏运用自己已掌握的句式的意识，而以自己头脑中拼凑的中式英语取而代之。其实，只要能恰当地运用上述的任何一个句式，考生的作文就会出现闪光点，就会取得比较好的成绩。