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
In retinoscopy for refractive error at lm we add -1 D. If done at a distance of 66 cm, the addition factor will be: 
Select and explain. 
A. -2D, B. -1.5 D, C. -0.5 D, D. -5 D
B: -1.5 D
Answer: B: -1.5 D 
Explanation: Ans. -1.5 D