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: Anaesthesia
Increased cardiac oxygen demand is caused by – 
Select and explain. 
A. Ketamine, B. Nitrous oxide, C. Thiopentone, D. Halothane
A: Ketamine
Answer: A: Ketamine 
Explanation: None