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
Which is the absolute contraindication of MRI? 
Select and explain. 
A. Pacemaker, B. Prosthetic cardiac valves, C. Insulin pump, D. Cochlear implants
A: Pacemaker
Answer: A: Pacemaker 
Explanation: MR imaging is contraindicated for patients with metal implants or foreign bodies, such as intracranial aneurysm clips, intraorbital metallic foci, cardiac pacemakers, or specific types of cardiac valves. In these instances, these objects may be dislodged or damaged by the magnetic field. MR imaging may also be contraindicated for claustrophobic or uncooperative patients who may not respond to conscious sedation protocols. Ref: Chen M.Y., Whitlow C.T. (2011). Chapter 1. Scope of Diagnostic Imaging. In M.Y. Chen, T.L. Pope, D.J. Ott (Eds), Basic Radiology, 2e.