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: Gynaecology & Obstetrics
[{'content': 'The earliest indication of concealed acute bleeding in pregnancy is : \nSelect and explain. \nA. Tachycardia, B. Oliguria, C. Postural hypotension, D. Low body temperature', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Tachycardia', 'role': 'assistant'}]