The right option is; b. comes from a variety of sources
Nonpoint source pollution refers to pollution that is produced from many sources such as atmospheric deposition, land runoff, precipitation, drainage, and seepage. Nonpoint source pollution is caused when rain falls, and its water moves over, and through the ground. The runoff moves, and picks pollutants (natural and human-made), and finally discharge them into water bodies such as lakes, rivers, and ground waters. Nonpoint source pollution is difficult to control because it comes from many sources.