Urea Agar Is Set Up for Quality Control Purposes Using

Multiple Choice

Urea agar is set up for quality control purposes using two Trichophyton spp.-T.mentagrophytes and T.rubrum.After the appropriate amount of incubation,both organisms are negative.Which one of the following statements explains this discrepancy?

A) The medium is most likely expired.
B) These two Trichophyton spp.are poor choices for quality control.
C) The phenol red indicator is not working because both organisms are positive for urea.
D) No discrepancy is present;both organisms are negative for urease activity.