This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2018, Subject name: Surgery
What is the name of the given instrument, used for harvesting the graft from healthy area in split thickness skin graft? 
Select and explain. 
A. Dermatome, B. Silver's knife, C. Catlin amputating knife, D. Humby knife
D: Humby knife
Answer: D: Humby knife 
Explanation: Humby Knife A knife with a roller attached, used for cutting skin grafts of varying thickness The distance between the roller and blade of knife can be varied by means of a calibration device.