D political liberty is the answer
Answer:
Climate Change
Explanation:
Some of the biggest human migrations coincided with major changes in climate, according to a new analysis. Researchers say early humans set out in search of climates where food was available. And some populations stayed put in certain locations because barriers like glaciers block their progress.
At the center of the Earth is the core, which has two parts. The solid, inner core of iron has a radius of about 760 miles (about 1,220 km), according to NASA. It is surrounded by a liquid, outer core composed of a nickel-iron alloy. The outer core is about 1,355 miles (2,180 km) thick.
