This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Circulation: Circulatory Shock and Its Treatment, Subject name: Physiology
[{'content': 'First response to decreased blood volume - \nSelect and explain. \nA. Increased heart rate, B. Tachypnea, C. Hypotension, D. Disorientation', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Increased heart rate Severity of decreased blood volume", 'role': 'assistant'}]