Q: Fact 1: Harming an animal species has a negative impact on the population size of that species. Fact 2: Pollution is usually harmful to one or more species of animal or plant. Given the two facts above, what is usually harmful to the population size of a species?

Choose from:
a). Pollution.
b). reproduction.
c). viruses.
d). disease.
e). habitat.
f). ecosystems.
g). influenza.
h). deforestation.
A:
a).