Olsen's hypothesis is that the Botai domesticated and rode horses instead of killing them to eat them. The last paragraph of the passage tells us that full skeletons were found in the caves, which makes Olsen think that they were domesticated and ridden. It would help to know how many of these kinds of untouched drones there were versus butchered horse bones. If there were only a few untouched horse bones and a lot of butchered horse bones, maybe those untouched bones were the exception (some horses just happened to die there) and the Botai ate their horses. Conversely, if there aren't a lot of butchered horse bones, it would seem to help support Olsen's hypothesis. Thus, (A) helps evaluate Olsen's hypothesis. Hope this helps!
