Occasionally, raw sewage is dumped directly into a lake or river. The major effect that this has on the water environment is that the: A.) oxygen content of the water drops
B.)aquatic plant growth decreases
C.)water becomes poisoned
D.)bacteria die

A.) oxygen content of the water drops

Explanation:

Sewage refers to waste from living organism like feaces and urine and it is considered a pollutant to any water body it is deposited. Pollutants affect the aquatic ecosystem. In this case, a raw sewage dropped in a river or lake will cause the oxygen content of that water body to be reduced.

This is because, microbes also called decomposers begin to act on the second pollutant in the water body. Their action accompanies the use of oxygen in thr water body for cellular respiration, hence, reducing the oxygen level readily available to the aquatic organisms.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."