The fact that a rabbit's immune system can recognize a human protein as foreign and create antibodies for it suggests that rabbits and humans share certain biological similarities, which points to a degree of evolutionary relationship. Specifically, it highlights the presence of similar or conserved proteins and immune system mechanisms across different species.
Given the options you provided, the correct answer is: c They have similar DNA.
This choice reflects that despite being different species, rabbits and humans share similarities at the genetic level that allow for such immune recognition.