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
The volatility of an anesthetic agent is directly proportional to lowering the flow in the portal vein. Portal flow is maximally reduced by – 
Select and explain. 
A. Ether, B. Halothane, C. Isoflurane, D. Enflurane
B: Halothane
Answer: B: Halothane 
Explanation: All volatile anaesthetic agents reduce portal hepatic blood flow. This decrease is greatest with halothane and least with isoflurane.