You are presented with the question "what causes the immune system to not work properly?" and the following answer choices: 
- HIV
 - lack
 - DDT
 - p53
 - antibiotics
 - h2o
 - memory cells
 - HPV

Now knowing that immunodeficiency occurs when the immune system is not working properly and hIV, the human immunodeficiency virus, is a retrovirus, choose the best answer.


 

 HIV        