You are presented with the question "What is usually harmful to the population size of a species?" and the following answer choices: 
- Pollution
 - reproduction
 - viruses
 - disease
 - habitat
 - ecosystems
 - influenza
 - deforestation

Now knowing that harming an animal species has a negative impact on the population size of that species and pollution is usually harmful to one or more species of animal or plant, choose the best answer.


 

 Pollution        