Doctor：You needn't go on a diet；but you must eat sensibly¹ 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 Drill²．

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 fatal³．

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。