This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
[{'content': "True statement about Jackson's Cross - Cylinder test is \nSelect and explain. \nA. Used for subjective refinement of spherical error, B. Most commonly uses -0.5D sphere with +0.5D cylinder, C. Uses spherocylindrical toric lens, D. All of the above", 'role': 'user'}, {'content': 'Answer: C \nExplanation: It is used for subjective refinement of cylindrical error. Most commonly uses -0.5D sphere with +1.0D cylinder.', 'role': 'assistant'}]