Why Is It Entirely Possible for a Pathogen to Appear

Why is it entirely possible for a pathogen to appear susceptible in susceptibility testing and resistant in a real- life context?

A) The ability of the pathogen to live as part of a biofilm and benefit from the protection of other bacteria does not exist in susceptibility tests.
B) Bacterial levels and active drug concentrations vary from one tissue to another in an active infection.
C) A real- life infection allows for the possibility of genetic crossover with different bacteria, whereas tests in the lab are focused on studying a single strain of bacteria.
D) A person's liver may break down the drug before it even begins to benefit the patient.
E) An active infection is more likely to mutate due to the larger population.