This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Surgery
Dye used in chromoendoscopy for detection of cancer 
Select and explain. 
A. Gentian violet, B. Toluidine blue, C. Hemotoxiline and eosine, D. Methylene blue
D: Methylene blue
Answer: D: Methylene blue 
Explanation: Chromoendoscopy is an endoscopic technique that uses stains during endoscopy to highlight differences in mucosa, as well as dysplastic and malignant changes that are not apparent in white light. Chromoendoscopy has been used in the evaluation of Barrett esophagus, esophageal adenocarcinoma, gastric metaplasia and adenocarcinoma, colon polyps , colon cancer, and surveillance in inflammatory bowel disease. Common staining agents used are Lugol solution, methylene blue (gastric metaplasia & carcinoma ), toluidine blue, crystal violet, indigo carmine, congo red, and phenol red.