Mình ko rõ yêu cầu bài nên mình nghĩ chắc dùng mệnh đề quan hệ nha
11 i thanked the woman who helped me.

12 the girl who won the race is happy

14the book which is on the table is mine

the mechanic who is repairing my car is my uncle

15 the building which was built on the side of the hill belongs to my father

16 the river which is not safe for swimming is polluted 

17that is the book which i bought yesterday 

18 is this the who you are waiting for

19the people which we invited two days ago were very nice

20 the police havent found the man who stole my car

21 the postcard which came this morning was from Harriet

22 the bus which runs every half our goes to the airport

23 the play which was written by shakespear were performed last night

24 easter is a joyful festival which is celebrated ....

25 the boy who is wearing jeans is my classmate

26 the bomb which went off this morning caused a lot of damage 

ko thay nua