You are presented with the question "Passive immunity decreases with" and the following answer choices: 
- ozone depletion
 - edema
 - passive-aggressive behavior
 - stellar implosion
 - stress
 - HIV
 - time
 - death

Now knowing that passive immunity lasts only as long as the antibodies survive in body fluids and furthermore, antibody levels decrease with time, choose the best answer.


 

       time  