Question

one of the biggest sources of water pollution is ______ *
brushing your teeth
taking showers
runoff (agricultural, municipal, etc.)
swimming

Explanation:

Brushing teeth, taking showers and swimming are not major sources of water - pollution on a large - scale. Runoff from agricultural (pesticides, fertilizers) and municipal (sewage, waste) sources is a significant contributor to water pollution.

Answer:

C. runoff (agricultural, municipal, etc.)