This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 1, Subject name: Physiology
[{'content': "Mouth-to-mouth breathing delivers_____% oxygen into the subject's respiratory system: \nSelect and explain. \nA. 8%, B. 10%, C. 16%, D. 20%", 'role': 'user'}, {'content': "Answer: C \nExplanation: In mouth-to-mouth breathing, exhaled air is delivered into the subject's respiratory system. This exhaled air is a mixture of dead space air (about 20% oxygen) and the alveolar air (about 10% oxygen). Hence, the delivered air contains about 16% oxygen, along with CO2 and nitrogen.", 'role': 'assistant'}]