题目内容：

Greater efforts to control the population must be made if food shortage____avoided.
Greater efforts to control the population must be made if food shortage____avoided.A.is to be B.can be C.

优质解答

AB都不对,和句子意思不符.选项不全.根据句子意思应选cannot be 意思是 如果食品短缺不可避免,必须在控制人口上作出更大努力.