Question

what environmental change allowed people to travel by land between asia and north america
○ human adaptation to arctic environments
● ice sheets blocking sea routes
○ the formation of ice sheets on land
○ the melting of ice sheets on land

Explanation:

During the last Ice Age, lower sea - levels due to large amounts of water being locked in ice sheets created a land bridge (Beringia) between Asia and North America, allowing human migration. Ice sheets blocking sea routes forced people to use this land route.

Answer:

ice sheets blocking sea routes