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
Which among the following anaesthetic increases the cerebral oxygen consumption? 
Select and explain. 
A. Alfentanil, B. Ketamine, C. Thiopentone, D. Propofol
B: Ketamine
Answer: B: Ketamine 
Explanation: Ketamine increases cerebral oxygen consumption and it also increases intracranial tension.