Topic 2

一、情态动词

You mustn't throw litter around.你严禁乱扔垃圾。

[点拨]

"情态动词"有can (could), may (might), must, have to, shall (should, will (would), dare (dared), need (needed), ought to等。

情态动词无人称和数的变化;不能单独使用，必须与其后的动词原形构成谓语。

本节主要讲must/mustn't,may,can.

must意为“必须”，语气较重。其否定形式为：needn't.

mustn't意为“禁止”may意为"可以;也许"can意为“能够;可能”