Fact 1: Immunodeficiency occurs when the immune system is not working properly.

Fact 2: Work items are broken down by year of effort.

Given the two facts above, answer the question "Immunodeficiency occurs when the immune system is what?" with the following options: 
- dangerous
 - homogenous
 - healthy
 - broken down
 - reduce
 - perfect
 - It decreases
 - functioning


 

    broken down     