This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Elementary Optics, Subject name: Ophthalmology
[{'content': 'Angle kappa is formed between which axes? \nSelect and explain. \nA. Anatomical and visual axis, B. Anatomical and horizontal axis, C. Between two visual axes, D. Visual axis and vertical axis', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. (a) Anatomical and visual axisRef: Kanski's 7/e, chapter 18", 'role': 'assistant'}]