Answer:
Mountains isolated many groups that migrated to the region. Dense forest served as a barrier to migration across the region. Vast plains facilitated the migration of people across the region.
Explanation:
CORRECT
I looked all over the Internet, and saw that there is another option that you didn't include, and which is actually the correct answer.
Bays best facilitate the building of ports, not these options.
It depends on the latitude where you measure it.
It's about 69 miles on the equator, and it shrinks to zero at the poles.
In general, at any latitude,
Distance covered by 1 degree of longitude =
<em> (69 miles) x [ cosine(latitude where it's measured) ]</em>
