竹一A-英文文法與習作(二) Exercise 9, p. 126

2. What did Mary see?
3. Who saw an accident?
4. Whom did Mary see?
5. Who saw John?
6. What happened?
7. What did Alice buy?
8. Who bought a new coat?
9. What are you looking at?
10. Whom are you looking at?
11. Whom did you talk to?
12. What did Tom talk about?
13. What did the teacher look at?
14. Who looked at the board?
15. Whom did the teacher look at?
16. What is a frog?
17. What is an amphibian?
18. What do frogs eat?