用所给单词的适当形式填空。

1. We often watch the students _____ (play) football after school.

2. Last night we _____ (eat) a big cake.

3. They had great fun _____ (play)  games.

4. I like them because they are very _____ (friend) to us.

5. Nobody _____ (be) in the classroom just now.

6. I have a _____ (real)  important presentation to make this afternoon.

7. It is _____ (rain)  these days,  so we will have to stay at home and watch TV.

8. —How're you _____ (feel) now?

    —Much better.

9. —Would you mind my _____ (smoke) here in this room?

    —Not at all.

10. Is anybody _____ (else)  composition better than this one?

当狗吃到食物时会分泌唾液，这属于( )。

A．条件反射

B．非条件反射

C．操作性条件反射

D．经典条件反射