This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
[{'content': "The test likely to help in diagnosis of a patient who presents with an itchy annular plaque on the face is: \nSelect and explain. \nA. Gram's stain, B. Potassium hydroxide mount, C. Tissue smear, D. Wood's lamp examination", 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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.', 'role': 'assistant'}]