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: Forensic Medicine
Which of the following factor determines extent of wound caused by a bullet? 
Select and explain. 
A. Size, B. Weight, C. Velocity, D. Shape
C: Velocity
Answer: C: Velocity 
Explanation: A bullet's ability to wound is directly related to its kinetic energy (E=mv2/2) at the moment of impact. Because kinetic energy increases in direct propoion to weight (mass) of the missile and the square of its velocity, a bullet travelling at twice the speed of a second bullet of equal weight and similar shape, possesses four times much energy or wounding power. Ref: The essentials of forensic medicine and toxicology by Dr K S Narayan Reddy, 27th edition, Page 189.