Which example is nonpoint-source pollution?

a. polluted rainwater

b. a factory discharging wastes into a river

c. smokestack emissions from a factory

d. sewage from an overflow pipe

First off, what is nonpoint-source pollution?

It comes from many sources BUT this type of pollution doesn't come from factories discharging their waster, nor sewage pipes, nor smokestack emissions; but rather it comes from rainfall or snow-melt moving through and over the ground. Taking away natural and human-made pollutants.

This being said, the answer, is A. Polluted Rainwater.

Density and pressure