Fact 1: Pathogens can cause disease.

Fact 2: The disease affects the immune system.

Given the two facts above, answer the question "What can affect the immune system?" with the following options: 
- pathogens
 - Pesticides
 - dirt
 - chickenpox
 - Allergies
 - viruses
 - odors
 - pollution


 

 pathogens        