Select from the following.
1). deforestation
2). repopulating them
3). Pesticides
4). hypothyroidism
5). kill them
6). harming them
7). light
8). helping them
Given those answer options, answer the question: Fact 1: Harming an animal species causes that animal 's population to decrease. Fact 2: Fish are wild animals. Given the two facts above, doing what to fish species causes their population to decrease?
A:
6).