sentence:
Look before you leap.
May I ask you a question?
May I have a receipt?
May I have your name,please?
May I pay by credit card?
pattern drill:
Don't....
You mustn't.....
for example: take this medicine,make a noise,talk in library..
key words and expressions:
two more days 再过两天
acquire 获得
hesitate 犹豫
