In which of the following situations might a bacteriostatic drug be preferable to a bactericidal drug?

A) when a patient is infected with an unknown pathogen
B) when the patient is immunocompromised
C) when antibiotics are being used prophylactically
D) when an infection is in a well-oxygenated region of the body
E) when Gram-negative bacteria have infected an ordinarily sterile region of the body