According to one theory when the glaciers disappeared birds ______.A.stopped migratingB.

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According to one theory, when the glaciers disappeared, birds ______.

A.stopped migrating

B.continued migrating

C.began migrating again

D.migrated south and stay there

请帮忙给出正确答案和分析,谢谢!

热搜:medline数据库中to字段是表示非英文文献的原文题名