Which of the following is NOT mentioned in the passage as influencing the migration of locusts?
A.Darkness.
B.Agricultural activities.
C.Warm air currents.
D.Overcrowding.

A.Darkness.
B.Agricultural
B.
C.Warm
C.
D.Overcrowding.

【参考答案】

A
解析：本题可以通过排除法找到答案。文中第一句说：“在美国农业活动破坏生态平衡之前，存在着落基山蝗虫的大量迁徙......

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