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
[{'content': 'A 50 year old lady is given methotrexate for severe rheumatoid disease causing joint pains and functional limitation. She also has to be given folinic rescue therapy. Which of the following is the mechanism by which methotrexate acts? \nSelect and explain. \nA. Increasing folic acid excretion, B. DNA binding, C. Binding to dihydrofolate reductase, D. Increasing nucleotide synthesis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Binding to dihydrofolate reductase', 'role': 'assistant'}]