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': 'SRK formula used to calculate power of IOL is ( A ⇒ IOL constant ,K ⇒corneal curvature, L  ⇒ axial length of eyeball) \nSelect and explain. \nA. A - 2.5k - 0.9 L, B. A - 2.5L - 0.9 k, C. 2.5A - L- 0.9K, D. L - 0.9L - 2.5K', 'role': 'user'}, {'content': 'Answer: B \nExplanation: SRK formula to calculate power of IOL\nPower = A\xa0→ IOL\xa0constant\nL\xa0⇒ axial length of eyeball given by A - scan USG\nK\xa0⇒ Corneal curvature by Kertometer.', 'role': 'assistant'}]