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.

用could, can, may, must, need't 填空。