The migration from Asia to North America across the Bering Strait (perhaps by land bridge) was a ________ event in human history.
句意：从亚洲到北美穿越白令海峡（也许是通过陆桥）的迁徙是人类历史上的一件大事。monumental里程碑式的。disastrous灾难的。physical生理的。evolving进化的。因此，本题的正确答案为A。