在英语语法中，关系代词和关系副词是构建定语从句的重要元素，而“as”作为一种特殊的关系代词或关系副词，在特定情况下用于引导定语从句。它具有独特的功能，能够灵活地连接主句与从句，表达出一种包含、类似或者伴随的关系。为了帮助大家更好地掌握这一知识点，本文将通过一系列练习题来加深理解。
一、基础概念回顾
1. as的基本用法
- 引导限定性定语从句时，as通常用来指代整个主句的内容，表示“正如……那样”。例如：
As we all know, the Earth revolves around the Sun.
（正如我们所知，地球围绕太阳运转。）
- 在非限定性定语从句中，as可以指代整个主句内容，并且位置灵活（可位于句首、句中或句尾）。例如：
The sun rises in the east, as everyone knows.
（太阳从东方升起，这是众所周知的事实。）
2. 区别于which的关键点
- “which”只能指代先行词，而“as”则更多用于指代整个主句内容。
- 非限定性定语从句中，“which”不能位于句首，但“as”可以。
二、实战练习
练习1：选择合适的引导词
请根据句子的意思，选择正确的引导词填入空白处：
1. She was late for school ________ she missed the bus.
A. because B. as C. which D. that
2. The book is very interesting, ________ I can’t stop reading it.
A. so B. as C. therefore D. which
3. He is honest, ________ makes him popular among his classmates.
A. what B. who C. that D. as
4. As a result of hard work, ________ he achieved great success.
A. which B. that C. where D. as
5. It rained heavily yesterday, ________ prevented us from going out.
A. when B. where C. as D. that
练习2：改写句子
将以下句子改写为使用“as”引导的定语从句：
1. The man is an expert, and he knows everything about computers.
→ The man, ________, knows everything about computers.
2. He is kind-hearted, and everyone likes him.
→ He is kind-hearted, ________.
3. The weather was terrible, and we couldn’t go hiking.
→ The weather was terrible, ________.
4. She is smart, and she always gets high scores in exams.
→ She is smart, ________.
5. We arrived at the station early, and we caught the train on time.
→ We arrived at the station early, ________.
练习3：判断正误
判断下列句子是否正确，若错误，请说明原因并改正：
1. As is known to all, the Great Wall is one of the seven wonders of the world.
（正确/错误）________
2. The reason why he failed is as he didn’t prepare well enough.
（正确/错误）________
3. As we discussed before, this project requires a lot of time.
（正确/错误）________
4. He has no money, as a result of which he cannot afford to buy a car.
（正确/错误）________
5. She is beautiful, as her mother says.
（正确/错误）________
三、答案解析
练习1答案：
1. B 2. B 3. D 4. A 5. C
练习2答案：
1. as is known to all
2. as everyone likes him
3. as prevented us from going hiking
4. as she always gets high scores in exams
5. as we caught the train on time
练习3答案：
1. 正确
2. 错误；应改为：The reason why he failed is that he didn’t prepare well enough.
3. 正确
4. 正确
5. 错误；应改为：She is beautiful, just as her mother says.
通过以上练习，相信你对“as”引导定语从句有了更深的理解。这种语法点虽然看似简单，但在实际运用中却需要结合具体语境仔细分析。希望大家能够在日常学习中多加练习，逐渐提高自己的语法水平！
