Human migration occurred because of several factors. The reasons are the following:
1.food shortages
2.War
3 Seasonal changes
4.Disease and epidemic.
Africans are nomadic people. They thrive more from their environment. They only had to stop migrating during the agricultural era, wherein they learn to plant and tend crops and started cattle herding.
The correct answer is A. Technological advances such as s<em>team power, air brakes, automatica lubricators and steel tracks</em> have affected the railroads very positively, since it has made it possible that the rail network could become a safer, more efficient and more reliable means of transportation for goods.
<span>The celestial equator </span>