1)a large number of men always around a girl who is my friend.

4)a girl was always arounded by a group of men ,the girl who is my friend 正確，意思是一群男人老是圍著一個女孩，那女孩是我朋友。

5)my brother always arounds a girl who is my friend

8)a girl was always arounded by my brother, the girl who is my friend 正確，我哥哥老是圍著一個女孩，那女孩是我朋友。

2)a large number of men always around a girl, the girl who is my friend.

6)my brother always arounds a girl, the girl who is my friend 錯誤，不應該加the girl 因為先行詞a girl 跟從句時緊挨的

7)a girl was always arounded by my brother who is my friend

3)a girl was always arounded by a group of men who is my friend 錯誤，這種情況應該加the girl 否則它就指代的是my brother ，a group of men 定語從句的構成 先行詞（名詞）+ 引導詞（關係代詞 關係副詞） + 定語從句 用結構分析，自己體味，語感也很重要的。