Nobody knows for sure how dinosaurs died out 65,000,000 years ago. It _______ because of sudden changes of their living conditions.
#62591
A
must have happened
B
would have happened
C
should have happened
D
might have happened
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—Will you stay for some more days? —Sorry, I_____. My mother called to ask me to go back at once.
#77550
A
mustn’t
B
may not
C
can’t
D
wouldn’t
It is required that under no circumstances ______ betray ourselves even if there are temptations like money or beauty.
#63636
A
we will
B
should we
C
we
D
we shall
—I regret to say that I failed to rank first in the terminal exam.—Come on，nobody ________ win all the time.
#62288
A
should
B
must
C
shall
D
can
---- May I smoke here?---- If you , choose a seat in the smoking section
#62881
A
should
B
could
C
must
D
may
We can make a fire ______ the room warm so that we can chat for a while.
#77591
A
to keep
B
keeping
C
keep
D
kept