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': 'The ratio of concentration of drug in co-trimoxazole of trimethoprim and surfamethoxazole is: \nSelect and explain. \nA. 1:02, B. 1:03, C. 1:05, D. 3:01', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 1:05', 'role': 'assistant'}]