单项选择，从A、B、C中选出最佳的答案。
1）----We never know _______ he wants.
----They say he wants a baby boy.
A.whom B.what C.which
2）He is thirsty.Please give him some _______to drink.
A.rice B.meat C.water
3）Don't forget to _______ thank you when someone has helped you.
A.speak B.say C.tell
4）They _______ their homework in the evening.
A. don't do B. don't C. not do