You are presented with the question "what can affect the respiratory system?" and the following answer choices: 
- Pollution
 - mildew
 - gas
 - influenza
 - oxygen
 - bacteria
 - smallpox
 - gold

Now knowing that amold spore has a negative impact on the respiratory system and mildew and mold spores are everywhere, choose the best answer.


 

  mildew       