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
Which is not an indication for walking bleach: 
Select and explain. 
A. Discolouration of the pulp chamber., B. Defective enamel formation., C. Dentin discolouration., D. None.
B: Defective enamel formation.
Answer: B: Defective enamel formation. 
Explanation: None