A principal criterion for the diagnosis of meningitis due to Neisseria meningitidis is ( ).
A.
Observation of acid-fast rods in the spinal fluid.
B.
Gram-negative cocci, arranged in pairs, in the spinal fluid.
C.
Gram-negative rods in the spinal fluid.
D.
Observations of mycoplasmas in the spinal fluid.
E.
Gram-positive rods in the spinal fluid.