I believe the answer is: increase in food supply and disease immunity.
Prior to 2000 years ago, society experience massive shortage in food supply which cause a lot of people died due to hunger which always keep the population low.
The fact that there is no vaccine also contribute to the low population because it cause a lot of death for infants and children before they grow up.
B is the correct answer.
To become the Chair of a committee in Congress, you really just need to stay on the Committee for the longest and have your party win control of the House.
<span> Chinese civilzation centered amost entirely around the Yellow River</span>
Please see below answer, I hope it helps you.
The motivation behind why was the logical insurgency an urgent time in history is a result of the changed in mankind's way to deal with understanding the regular world and prompted new revelations.