在英语学习中，定语从句是一个重要的语法知识点，它能够帮助我们更精确地描述名词或代词。为了更好地掌握这一语法点，以下是一些适合初中阶段学生的练习题及其答案。

一、单项选择

1. The book ______ I borrowed from the library is very interesting.

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

答案：B. which

2. The man ______ you talked to just now is my uncle.

A. that B. what C. where D. when

答案：A. that

3. The girl ______ is standing under the tree is my friend.

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

答案：B. who

4. The movie ______ we watched last night was fantastic.

A. what B. who C. that D. whose

答案：C. that

5. This is the house ______ I used to live in.

A. where B. which C. that D. whose

答案：A. where

二、填空题

6. The boy ______ helped me with my homework is my classmate.

7. The school ______ we visited last week is very famous.

8. The car ______ broke down on the road belongs to my father.

9. The book ______ you gave me is very useful.

10. The teacher ______ spoke at the meeting is very kind.

三、改写句子

11. The girl is reading a book. (改为定语从句)

The girl who is reading a book is my sister.

12. The book is on the table. (改为定语从句)

The book which is on the table is mine.

13. The man is walking in the park. (改为定语从句)

The man who is walking in the park is my father.

14. The classroom is big. (改为定语从句)

The classroom which is big is ours.

15. The pen is in the drawer. (改为定语从句)

The pen which is in the drawer is hers.

通过以上练习，我们可以更好地理解和运用定语从句。希望这些题目能帮助大家巩固相关知识，提高英语水平。如果还有疑问，可以随时查阅相关资料或请教老师。