The principle difference between point source and nonpoint source water pollution is .

b. the number of sources of pollution

Explanation:

The U.S. Environmental Protection Agency (EPA) describes the point source pollution as “any particular identifiable cause of pollution from which pollutants are released, such as a channel, ditch, boat or factory chimney”. Factories and sewerage treatment of plants are two well-known types of point sources.

The distinction between the point and non point source pollution is that point cause of pollution which has a single origin or source while non point source pollution is a combination of pollutants from various origins, and not all of them are easily identified.

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.