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
Which of the following is an inhibitor of dihydrofolate reductase? 
Select and explain. 
A. Phenytoin, B. Alcohol, C. Yeast, D. Methotrexate
D: Methotrexate
Answer: D: Methotrexate 
Explanation: Drugs causing folate deficiency