Why does the government not do more to regulate nonpoint source pollution?
a. nonpoint source pollution is less harmful to the environment, so it does not need to be regulated.
b. point source pollution is more common than nonpoint source pollution, so it is more regulated.
c. nonpoint source pollution is caused solely by animals, which are not possible to regulate.
d. nonpoint source pollution is difficult to regulate, because its source is difficult to track.

d. Nonpoint source pollution is difficult to regulate, because its source is difficult to track.

The non point source pollution is a pollution which is caused by the rain or snow melt which takes away natural and human made pollutants from the land  by surface run off and deposits these pollutants into the water body such as lakes, ponds, rivers and other wetlands. These pollutants gets aggregated in the water body and their source of origin cannot be traced back. Therefore, the nonpoint source pollution cannot be managed or reduced by the government.

Hence, d. Nonpoint source pollution is difficult to regulate, because its source is difficult to track is correct option.

b would be the right answer