—May I go to the science museum with you next Saturday?
—You can't ________you have a ticket. I have only one ticket.

A: May I go out to play football, Dad?

B: No, you ________. You must finish your homework first.

A. may not?????? B. needn’t????????? C. shouldn’t?????? D. mustn’t

Bill is a lovely boy. He is four years old. There is a park near   1___  house. It is small but beautiful. He  2  with other children in the park every day.
One day, his mother buys new clothes for him.    3   clothes are nice and expensive. Bill is very happy.
“Mum, may I go out     4  play with my friends? I want to show them my    5   clothes.” Asks Bill.
“Yes, please keep your clothes clean.” Says his mother, “I'm going to do some cooking. We will have    6  after your father comes back.”
At about six his father comes back  7   work. Bill goes home for dinner.
“Why do you have so much dirt（泥土）on your  8   ? ” asks his mother when Bill comes into the room..
“Because I have some falls （跌倒）”, answers Bill.
“You mustn't have some falls when you    9   the nice clothes,” says his mother.
“I'm sorry, Mum,”   0   Bill. “But I have no time to take off my clothes when I fall.”

  —May I go out to play soccer ball?

—I’m afraid not. You can’t play __ you have finished your homework.

A．after             B．when             C．of               D．unless