1 . Love is one of the greatest things in the world, but sometimes it ______ be difficult.

A．would

B．can

C．should

D．must

2 . Cats ________ be quite friendly towards humans, but they live mysterious lives of their own.

A．need

B．must

C．shall

D．can

3 . —Is there a holiday recently?
—There_____ be. It has been informed that we will continue to study for another three weeks.

A．won’t

B．mustn’t

C．may not

D．can’t

4 . Most American children go to state schools, but the private schools ______ be very good.

A．must

B．can

C．should

D．may

5 . Don’t answer the phone when the cell phone is being charged, for it ________ be very dangerous sometimes.

A．shall	B．should
C．can	D．must

6 . Mountain climbing ______ be really dangerous at times even though it is challenging and exciting in general.

A．can

B．should

C．shall

D．must

7 . Despite the fact that Lucy is a lovely girl, she _____ be extremely difficult to work with sometimes.

A．must

B．should

C．would

D．can