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: Anaesthesia
Methemoglobinemia can be treated by: 
Select and explain. 
A. Methylene blue, B. Vitamin K, C. Vitamin A, D. All of the above
A: Methylene blue
Answer: A: Methylene blue 
Explanation: Hepatic metabolism of prilocaine generates O-toluidine, which oxidizes hemoglobin to methemoglobin. Methemoglobinemia, if severe, may be treated by the intravenous administration of methylene blue Ref: Miller's anesthesia-7th ed, Chapter 30.