问题
选择题
Great efforts___________grain production must be made if food shortages are to be avoided.
A．to have increased
B．increased
C．to increase
D．to be increased
答案
答案：C
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Great efforts___________grain production must be made if food shortages are to be avoided.
A．to have increased
B．increased
C．to increase
D．to be increased
答案：C