Which of the following contributes to nonpoint source pollution in water?
a.
automobiles
b.
oil refineries
c.
paper mills
d.
water treatment plants

a.  automobiles

Explanation:

A non-point source pollutant is the one whose origin is unknown and cannot trace back to it's origination point. As the pollutant cannot be trace back it cannot be prevented from release and contaminating the environment.

The automobiles is the correct option because land or water vehicles may discharge oil or other emission products which cannot be trace back to the point of origination of the pollutant.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!