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
Most characteristic finding of retinitis pigmentosa: 
Select and explain. 
A. Ring scotoma, B. Peripheral field defect, C. Central scotoma, D. Diplopia
A: Ring scotoma
Answer: A: Ring scotoma 
Explanation: A i.e. Ring scotoma