在英语学习中，定语从句是一个非常重要的语法知识点，尤其对于初中阶段的学生来说，掌握好这一语法点能够帮助他们更清晰地表达复杂句子结构。为了更好地理解和运用定语从句，下面提供了一些基础且实用的练习题供同学们参考。

练习题一：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格：

1. The book ________ I bought yesterday is very interesting.

A. who B. whom C. which D. whose

2. This is the man ________ helped me with my homework last night.

A. which B. what C. whom D. that

3. Do you know the girl ________ is standing over there?

A. which B. who C. what D. where

正确答案：1.C 2.D 3.B

练习题二：改写句子

将以下句子改写成含有定语从句的形式：

1. Tom is a student. He studies hard.

改写为：__________

2. Lucy is a teacher. She teaches English.

改写为：__________

3. The book is on the table. It belongs to me.

改写为：__________

提示：使用适当的引导词来连接主句和从句。

练习题三：判断正误

判断下列句子是否正确，并说明理由：

1. The boy who is wearing a red shirt is my brother.

（正确/错误）

2. The pen which I used yesterday was lost.

（正确/错误）

3. The people whom we met at the party were all friendly.

（正确/错误）

通过以上练习题，相信同学们对定语从句有了更深的理解。定语从句的学习不仅需要记忆相关的规则，还需要多做练习以巩固所学知识。希望这些题目能帮助大家提高英语水平！