Great efforts to increase grain production if food shortages are to be avoided.
A. could be made
B. must be made
C. might be made
D. would be made
网友回答
A. could be made
(答案→)B. must be made
C. might be made
D. would be made
解析：考查情态动词的用法。句意“如果要避免食物短缺，就必须尽最大努力来提高谷物产量。”make great efforts to do sth.“尽很大努力做某事”；could和might意为“可以”，语气不强，must表示“必须”。故选B。