用括号内所给单词的适当形式填空。

1. Two American                       (visit) will come to our school.

2. We'll learn the ____________ (twelve) unit next week.

3. Why are you so ____________ (forget) , Mike?

4. The yellow River is the second ___________(long) river in China.

5. I'm ____________ (true) sorry to hear that.

6. There are some children ____________ (play) football on the playground.

7. The ____________ (man) names are Li Ping、Wang Lin and Yang Li .

8. This book is mine. That one is____________ (they).

9. The cat wanted to be on the side of the ____________ (win).

10. Three                       (five) in our class are boys.

People who listen to Hawking's lecture sometimes find ____ difficult to understand him. [ ]

A. him

B. that

C. it

D. its