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: Radiology
As absolute contraindication of MRI is: 
Select and explain. 
A. Pacemaker, B. Prosthetic cardiac valves, C. Insulin pump, D. Cochlear implants
A: Pacemaker
Answer: A: Pacemaker 
Explanation: Pacemaker