1 . People liked O. Henry’s stories, because simple as the tales were, they ______ finish with a sudden change at the end, to the readers’ surprise.

A．could

B．would

C．might

D．must

2 . If someone happens to have high fever and pneumonia, he or she _________ seek treatment fast.

A．must

B．needs

C．may

D．could

3 . Timmy, why        in the mud? I have already told you so many times not to!

A．must you sit

B．should you sit

C．will you sit

D．can you sit

4 . During the special period of fighting against the infective illness, you ________ wear a mask when going out.

A．must

B．can

C．need

D．may

5 . Just as I was hurrying to class, there ________ come Tom with a long story to tell you.

A．could

B．must

C．might

D．would

6 . It’s red light now. We _________stop and wait.

A．can

B．must

C．should

D．might

7 . Public health experts kept telling citizens it was of utmost importance that social distancing and hygiene habits ________ amid the pandemic.

A．were to be kept	B．had to be kept
C．must be kept	D．should be kept