You are presented with the question "what sometimes lives on the surface of their host?" and the following answer choices: 
- lungs
 - an organism's body
 - human
 - barnacles
 - fleas and ticks
 - density
 - sensory neurons
 - bacteria

Now knowing that some parasites live on the surface of their host and fleas and ticks are parasites, choose the best answer.


 

     fleas and ticks    