题目

---Do you know __________? ---I’m not sure. Maybe he is a teacher. A. what the man with glasses is B. what is the man with glasses C. who the man with glasses is D. who is the man with glasses 答案：A一束光由空气入射某介质，折射光线恰好与反射光线垂直，则该介质中的折射率为；则入射角为多少？