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: Surgery
[{'content': 'One of the following is earliest indication ofconcealed acute bleeding - \nSelect and explain. \nA. Tachycardia, B. Postural HT, C. Oliguria, D. Cold clammy fingers', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]