The test likely to help in diagnosis of a patient who presents with an itchy annular plaque on the face is:
B i.e. KOH mount Trichophyton rubrum is most common cause of tinea corporis (body), t. cruris, t. pedis, t. manuum & t.unguiumQ. Diagnosis is made by KOH wet mount.
Gram's stain
Potassium hydroxide mount
Tissue smear
Wood's lamp examination