The Decarboxylase Control Tube Inoculated with a Suspected Non-Fermenting Gram-Negative

The decarboxylase control tube inoculated with a suspected non-fermenting gram-negative rod is a turbid dirty gray color after incubation at 35°C in ambient air for 24 hours. This result

A) renders all decarboxylase results invalid.
B) is acceptable and the decarboxylase results can be read.
C) indicates the tube was probably not inoculated.
D) should be read at 48 hours not 24 hours.