—How often do I need to feed the birds?
问题:
—How often do I need to feed the birds?
—They ________ food every day,or they will be hungry.
A.must give
B.mustn’t give
C.must be given
D.mustn’t be given
—How often do I need to feed the birds?
—They ________ food every day,or they will be hungry.
A.must give
B.mustn’t give
C.must be given
D.mustn’t be given