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: Dental
A twenty year old female patient comes to the clinic with discoloration of the upper right central incisor. This tooth was intact and otherwise asymptomatic.

Bleaching is indicated in which of the following clinical situations 
Select and explain. 
A. Dentin discolorations, B. Teeth with discolored composites, C. Tooth discoloration due to caries, D. Teeth with superficial discolorations
A: Dentin discolorations
Answer: A: Dentin discolorations 
Explanation: None