They carry oxygen to your entire body, and carry carbon dioxide away from your body to be exhaled.
Environments are always changing so organisms need to adapt to survive. The organisms that survive are the ones that are fit to live in that environment, which is where survival of the fittest comes into play.
The answer would be C
The mold is most likely an antibiotic which produces substances harmful to the strain of bacteria and therefore any bacteria in its zone of inhibition will die as a result
hope that jhelps