把下列简单句改为带有定语从句的复合句. 1.The boys playing tennis are my friends. 2.He had a letter written in French 3.She is the girl called Mary 4.I know the boy running in the park
The boys who are playing tennis are my friends. He had a letter which was written in French. She is the girl who is called Mary . I know the boy who is running in the park