Please do not feed the fish; they _____ die if they eat too much.
[ ]
A. shall
B. must
C. need
D. may
B. must
C. need
D. may
It ______ be the postman at the door. It's only six o'clock.
[ ]
A. mustn't
B. can't
C. won't
D. needn't
B. can't
C. won't
D. needn't