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: Pathology
Red or brown discoloration of teeth is seen in 
Select and explain. 
A. Porphyra, B. Internal resorption, C. Nasmynth membrane, D. Silver
A: Porphyra
Answer: A: Porphyra 
Explanation: None