Mountain building is answer
Experts point to the impact of certain physical features, such as landforms, climates, and natural vegetation. ... If you live in the mountains, you're likely to develop a particular culture that adapts to life at a high altitude.
I think its A. small contained climates that differ from areas surrounding them
hope this helps XD
Idk A drought or not enough water?
Population density is the study of how many people live in some area as compared to other areas - this helps for example predict whether the area can preduce enough food for itself. It is measured in the number of people per a unit of area.
The correct answer then is:
<span> the number of people who live in a square mile or kilometer</span>
