Answer:
A. A biofilm
Explanation:
Biofilms have high bacterial density near to 10000000 CFU/ml bacteria. Due to such high densities, these biofilms becomes resistant to the antibiotics. These biofilms are basically community of microorganisms which stick itself to some kind of surface be it living or non-living. The bacteria’s which get attached to these biofilm and grow in an environment in which they possess both tolerance and resistance towards any bactericidal agent. Due to this functional mechanism of bacterias with in the biofilm, they become resistant to antibiotics.
