147 need not，must not 和 must 用于现在时和将来时

Doctor：You needn't go on a diet；but you must eat sensibly and youmustn't overeat．

医生：你不必节食，但要饮食有度，不能吃得过饱。

Zoo notice：Visitors must not feed the animals．

动物园通告：参观者不得给动物投喂食物。

Railway notice：Passengers must not walk on the line．

铁路通告：旅客不得在铁路线上行走。

You mustn't drive fast．There is a speed limit here．

你不能开快车。这地方有速度限制。

You needn't drive fast．We've plenty of time．

你不必开得快。我们时间足够。

You needn't strike a match．I can see well enough．

你不用划亮火柴。我可以看清。

You mustn't strike a match．This room is full of gas．

你不能划火柴。这屋里满是煤气。

School notice：The lifts must not be used during Fire Drill．

学校通告：在消防演习期间禁止使用电梯。

You mustn't wear that dress again．You look terrible in yellow．

你别再穿那套裙装了。你穿黄色难看极了。

Teacher：You needn't read the whole book but you must read the first four chapters．

老师：你们不必把整本书全读完，但必须读完前四章。

You must cut down that dead tree or it will fall on your house．

你必须把那棵死树砍了，否则它会倒在你的屋顶上。

Doctor：You mustn't take more than two of these pills at once．Three might be fatal．

医生：这些药你每次服用时不得超过两片。服三片就可能有生命危险。

Doctor（to patient's wife）：If the pain has gone he needn't take any more of these．

医生（对患者的妻子）：如果疼痛已经消失了，他就不必再服这些药片了。