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
SRK formula used to calculate power of IOL is ( A ⇒ IOL constant ,K ⇒corneal curvature, L  ⇒ axial length of eyeball) 
Select and explain. 
A. 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
B: A - 2.5L - 0.9 k
Answer: B: A - 2.5L - 0.9 k 
Explanation: SRK formula to calculate power of IOL
Power = A → IOL constant
L ⇒ axial length of eyeball given by A - scan USG
K ⇒ Corneal curvature by Kertometer.