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
The ratio of concentration of drug in co-trimoxazole of trimethoprim and surfamethoxazole is: 
Select and explain. 
A. 1:02, B. 1:03, C. 1:05, D. 3:01
C: 1:05
Answer: C: 1:05 
Explanation: 1:05