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
Folic acid metabolism is inhibited by :  a) Sulfonamides b) Methotrexate c) Nitrous oxide d) Trimethoprim e) 5–Flucytosine 
Select and explain. 
A. acd, B. abd, C. bde, D. ace
B: abd
Answer: B: abd 
Explanation: None