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: Social & Preventive Medicine
A 4 year old child was brought in Pediatric OPD with complaint of inability to see at night for the last few days, Pediatrician suspected deficiency of vitamin. Although the clinical signs of vitamin A deficiency are rare, but if occurred, what would be the first clinical sign? 
Select and explain. 
A. Retinal detachment, B. Bitot spot, C. Conjuctival xerosis, D. Corneal xerosis
C: Conjuctival xerosis
Answer: C: Conjuctival xerosis 
Explanation: None