1 . Lack of sleep _______ lead to weakened immunity and memory, and also slow physical growth.

A．shall

B．must

C．should

D．can

2 . English is a language that many people around the world ___________ not speak perfectly but ___________ at least understand.

A．may; can	B．would; might
C．will; must	D．could; might

3 . — You must be looking forward to your trip to Sydney.
— Yes. I         wait any longer.

A．can't

B．mustn't

C．needn't

D．shouldn't