A) Biological, physical, and chemical.
b) Physical: sediment radioactive material and heat.
c) Chemical: organic/inorganic: heavy metals, nutrients & pesticides.
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.
"Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor."
https://www.britannica.com/science/benzaldehyde
https://en.wikipedia.org/wiki/Benzaldehyde