Great efforts to increase agricultural production must be made if food shortage avoided.
A. is to be
B. can be
C. has been
D. will be
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(答案→)A. is to be
B. can be
C. has been
D. will be
解析：考察将来时表达法。本句中的条件句中使用be to do sth表示将来时，表示的强制要求做某事。句意：如果食物短缺要被避免，我们就要做出巨大的努力来增加农业的产量。故A正确。