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
What is the power of a lens if the focal length is 0.75m? 
Select and explain. 
A. 1 D, B. 1.3 D, C. 2 D, D. 2.3 D
B: 1.3 D
Answer: B: 1.3 D 
Explanation: Power = 1/Focal length
= 1/0.75
= 4/3
= 1.3D