This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skin Lesions And Disorders Of Pigmentation, Subject name: Skin
Twelve-year-old boy with vesicle over lip. Investigation to be done is: 
Select and explain. 
A. KOH mount, B. Tzank smear, C. Diascopy, D. Woods lamp
B: Tzank smear
Answer: B: Tzank smear 
Explanation: Ans. b. Tzanck smearHerpes labialis occurs due to HSV-I injection on Tzanck smear shows, multinucleated giant cells (MNGC).