Ⅰ、1、Their
2、our
3、Thses
4、Her
5、Its
6、His
Ⅱ、7、These are,friends
8、Who are
9、What is,job
10、Are they,they aren't
11、What are,sisters',jobs
Ⅲ、12-15:B C B B
16-20:C A A C C
Ⅳ、21、C mother——mother's
22、B is——are
23、B me——I
24、B a——an
25、C buses——bus