Fact 1: Roundworms may be free-living or parasitic.

Fact 2: Dogs remain susceptible to reinfection with hookworms and roundworms.

Given the two facts above, answer the question "Dogs remain what to free-living or parasitic species?" with the following options: 
- hungry for
 - warm-blooded
 - susceptible
 - fertile
 - taken over by
 - more abundant
 - Animal survival
 - friendly towards


 

   susceptible      