Question

which source of pollution would be hardest to trace and control?
a. runoff from a city
b. runoff from a mine
c. an oil leak from an ocean tanker
d. water from a factory discharge pipe

Explanation:

Non - point source pollution (such as runoff from a city, runoff from a mine) is harder to trace and control compared to point source pollution (like an oil leak from an ocean tanker, water from a factory discharge pipe). Runoff from a city (Option A) is a non - point source as it comes from multiple, diffuse areas (e.g., streets, rooftops) over a large area.

Answer:

A. runoff from a city