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
A 7 years old boy presented with painful boggy swelling of scalp, multiple sinuses with purulent discharge, easily pluckable hairs and lymph nodes enlarged in occipital region. Which one of the following would be most helpful for diagnostic evaluation? 
Select and explain. 
A. Bacterial culture, B. Biopsy, C. KOH mount, D. Patch test
C: KOH mount
Answer: C: KOH mount 
Explanation: Ans. c. KOH mount