—How often do I need to feed the birds?—They food every day or they will be hungry.A. mus

问题补充：

—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

答案：

A. must give

B. mustn’t give

(答案→)C. must be given

D. mustn’t be given

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