Question

where is the most polluted part of a river? farthest downstream farthest upstream

Explanation:

Pollution in a river accumulates as water flows downstream. Pollutants from upstream sources (like industrial waste, sewage, or agricultural runoff) get carried along and can accumulate or combine with more pollutants as the river moves downstream. So the farthest downstream part of the river tends to have the most pollution.

Answer:

A. Farthest downstream