What is a reason why earthquakes happen?
A. Earths mantle is below the crust.
B. Fault's break the Earths crust.
C. Tectonic plates slip up.
D. Waves shake the ground

it's C.

Explanation:

d. stage 4

explanation:

the existence of some kind of demographic transition is widely accepted in the social sciences because of the well-established historical correlation linking dropping fertility to social and economic development.[1] scholars debate whether industrialization and higher incomes lead to lower population, or whether lower populations lead to industrialization and higher incomes. scholars also debate to what extent various proposed and sometimes inter-related factors such as higher per capita income,lower mortality, old-age security, and rise of demand for human capital are involved.[2]