用could, can, may, must, needn't填空。
1. A: _______you answer the question in English?
B: Sorry, I_______._______I answer it in English.
A: No, you _______.You _______answer it in Chinese.
2. A: _______I ask a question?
B: Yes, you________. But you _______wait a minute.
3. A: _______I use your eraser, Bill?
B: Sorry. I don't have one. Ask Mary. She _______ have one.
4. A: _______you help me do the shopping?
B: OK. Sure.
5. A: _______you sweep the floor?
B: But_______ finish my homework first.
A: OK. You_______ do it at once.
