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: Physiology
[{'content': 'Normal gastric juice contains all except \nSelect and explain. \nA. Na+, B. K+, C. Ca++, D. Mg++', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Contents of gastric juice\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Cations\n\nNa+\nK+\nMg+2\nH+\n\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Anions\n\nCl-\nPO4-2\nSO4-2\n\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Pepsin\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Gastric lipase\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Mucus\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Intrinsic factor of Castle', 'role': 'assistant'}]