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
Theophyline levels in blood are increased by: 
Select and explain. 
A. Barbiturates, B. Methotrexate, C. Cimetidine, D. All of the above
C: Cimetidine
Answer: C: Cimetidine 
Explanation: Cimetidine