You are presented with the question "Doing what to fish species causes their population to decrease?" and the following answer choices: 
- deforestation
 - repopulating them
 - Pesticides
 - hypothyroidism
 - kill them
 - harming them
 - light
 - helping them

Now knowing that harming an animal species causes that animal 's population to decrease and fish are wild animals, choose the best answer.


 

      harming them   