What is non-point source pollution, and why is this kind of pollution hard to monitor and control?

Answer 1

non-point pollution is just what it sounds like (pollution with no specific point of origin) in contrast a point source would be pollution that comes from a known input like a factory. Non-point pollution could be run-off from agriculture or urban areas.
It is difficult to control because it affected by so many activities such as, road maintenance, construction of buildings, agriculture, or something as simple as washing your car in the driveway.

Answer 2

Do your own homework.