This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Pathology
A 60-year-old man is found in a state of disorientation and is brought to the emergency room in a comatose state. He lived alone, ate poorly, and drank large amounts of hard liquor. Physical examination reveals an emaciated man with a distended abdomen, jaundice, ascites, and a slightly enlarged liver and spleen. What blood test would confirm a diagnosis of hepatic coma? 
Select and explain. 
A. Alanine aminotransferase, B. Alkaline phosphatase, C. Ammonia, D. Bilirubin
C: Ammonia
Answer: C: Ammonia 
Explanation: Hepatic encephalopathy The development of hepatic encephalopathy is caused by increased serum concentrations of neurotoxic substances, eg: ammonia. -Choices A, B, and D are elevated in a variety of liver diseases but are unrelated to hepatic encephalopathy. Grading of Hepatic Encephalopathy Grade Features 1 Poor concentration Slurred speech Slow thinking Abnormal sleep rhythm 2 Drowsy but easily arousable Occasional aggressive behavior Lethargic 3 Confusion Drowsy Sleepy but responds to pain and voice Gross disorientation 4 Unresponsive to voice May or may not respond to painful stimuli Unconscious