Why would the scientist want to compare the DNA in the fur from the uncontaminated wolf den to fur from wolves in the exclusion zone?

Hi. Your question is incomplete. Unfortunately you did not submit the experiment to which this question refers, which makes it impossible for your question to be answered. However, I will try to help you as best I can.

It is likely that the scientist in this experiment decided to compare the DNA of the wolves presented in the question above, because he wanted to evaluate how the variables in this experiment acted in relation to the different treatments. This comparison is the basis for the scientist to determine the results of the experiment and to assess the differences in the experimental treatments.

In that case, to answer this question, you must read your experiment and identify the variables and treatments, and determine how these wolves fit into each treatment.

In an experiment, the treatments are the groups where the variables are tested, whereas the variables are the elements of interest to be studied.

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.