In Which Situation Below Is Rapid Bacterial Antigen Testing in a Suspected

In which situation below is rapid bacterial antigen testing in a suspected case of meningitis the optimal course of action?

A) When the patient has already been stared on antibiotic therapy.
B) When the cerebrospinal fluid is visibly cloudy with red blood cells.
C) When the Gram stain of the cerebrospinal fluid is positive.
D) When the cerebrospinal fluid is visibly cloudy with white blood cells.
E) When the Gram stain of the cerebrospinal fluid is negative.