Ответ:

1 eat

2 ate

3 are, eating

4 did,eat

5 will, eat

6 isn't eating, is going to eat

7 have, eaten

8 eats

9 have eaten

10 did, eat

11 eat

12 was eating

13 eats

14 eat

15 eats

16 has, eaten

17 have, eaten

18 has,eaten

19 will eat

20 did ,eat