Anyone pls help don’t know what it is

The answer is "Flooding rivers".

Explanation:

Floods can happen in rivers also, especially around waterway curves and meandering when fluxes surpass the bandwidth. Businesses and homes are often destroyed by floods while they're on the streams' native flood plains.

In terms of developing civilization, the floods formed the most important part of the topography of Fertile Crown because the floodwaters would create silt and good land. This one is employed for the cultivation and sustenance of rising societies.

porter is writing economic history because he is focusing on the cost of developing vaccines.

formulating the initial idea for the policy

answer is c.