B) Natural selection favored rabbits that are resistant to this virus.
Explanation:
Natural selection favors individuals that are more fit to survive in its environment so if a rabbit is resistant to the virus it would make sense for the other rabbits that are resistant to it to survive and reproduce, giving birth to more virus resistant rabbits.
The correct answer is B. The electrons deal with most of the spectrum emissions. Whilst mass is technically a factor, the more precise answer would be B.