Could, mustn´t or needn´t

Choose could, mustnīt or neednīt.

1. You open the present. It´s not your birthday yet.
2. I pack a big bag. A small bag is okay.
3. He write a long story. A short story is okay!
4. you please help me to carry the bags?
5. I read the email. It isn´t mine.
6. The man needn´t leave for Manchester yet. It´s too early.
7. You feed the tigers.
8. I act in the school play but I don´t want to.
9. The girls buy crisps for the party. They have enough.
10. We go window shopping. What do you think?