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': 'To cause hemorrhagic shock, least volume of blood loss should be: \nSelect and explain. \nA. 30%, B. 40%, C. 20%, D. 50%.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans: C (20%) Ref: Klingensmith ME, Chen LE, Glasgow SC, Goers T4. Melby SJ, Reticular Formation, EEC and sleep. In: Washington Manual of Surgery. 5th Edn, Lippincott Williams & Wilkins 2008; 7: 145Explanation: (See the following table)', 'role': 'assistant'}]