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: Pharmacology
Drug used to counteract Methotrexate toxicity: 
Select and explain. 
A. Mesna, B. Folinic acid, C. Folic acid, D. Vit B12
B: Folinic acid
Answer: B: Folinic acid 
Explanation: Folinic acid