I'm totally lost with this question. So when the Hvirus inserts itself into a chromosome of an animal, fragments of the virus are passed onto the descendants. The zebra finch and junco both have the hvirus fragments in the same location. They diverged 25 millions years ago, so therefore the hvirus is 25 million years old.
I just can't see any assumptions the argument is making. In my opinion, C might weaken the argument if the insertion occurs at a random spot. Doesn't this contradict that the fragments are in the same location?
Thanks!