I think the answer to this is B
Gene pool
Sum of a population's genetic material at a given time.
The term typically is used in reference to a population made up of individuals of the same species and includes all genes and combinations of genes (sum of the alleles) in the population.
D. living things as a reservoir
The answer is B. Bacteria blooms and decreased underwater photosynthesis causes asphyxia, killing the fish.
HOPE THIS HELP!
