B.
genetic variation causes antibiotic resistance
Antibiotics, in one way or another, come from bacteria and fungi themselves. These antibiotics are produced naturally by the bacteria and fungi to eliminate competition with other bacteria present. With such great discovery in this endeavor, many lives were saved. It was not long that bacteria found ways to be resistant to antibiotics. Bacteria that was found on frozen dead bodies are resistant to modern antibiotics. There are two currently known ways as to how bacteria builds resistance against antibiotics. One would be mutation. Due to continued exposed to the antibiotic, the bacteria would adapt to it and cause themselves to mutate to combat antibiotic. The second one would be the swapping of DNA or as what scientists call the horizontal gene transfer. This only applies though to some or few bacteria that already has this feature built-in to them.
