This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hyper Pigmented Disorders, Subject name: Dental
Which is the most effective topically applied bleaching agent? 
Select and explain. 
A. Tretinoin, B. Hydroquinone, C. Salicylic acid, D. Toc
B: Hydroquinone
Answer: B: Hydroquinone 
Explanation: Hydroquinone is most effective topically applied bleaching agent. It bleach freckles and lentigens but not cafe-au-lait spots or pigmented nevi.