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 –a) Ring scotomab) Peripheral field defectc) Central scotomad) Diplopia 
Select and explain. 
A. ac, B. a, C. ad, D. ab
D: ab
Answer: D: ab 
Explanation: Ring scotoma is a peripheral field defect, which is characteristic finding of retinitis pigmentosa.

"Peripheral vision loss is hallmark of retinitis pigmentosa, with the classic ring scotoma 30 -50 degree from fixation" __ Pediatric retina by Hartnett.
"The ring scotoma is the characteristic field defect of retinitis pigmentosa". —Harley's pediatric ophthalmology