There may be some strains of bacteria that are naturally resistant to these antibiotics, or there may be some that mutate to become resistant. This means that as antibiotics are used more and more, those that can be killed using the antibiotics die out, but those that are resistant will remain, and will reproduce. Over time, it will be the resistant species that predominate.
I think it's C. Because hibernation is usually for animals living in Continental climates. I basically just eliminated the other answers until I got that one. One example for animals living in cold climates burrowing are Arctic Foxes.