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
Cross resistance to macrolides is because: 
Select and explain. 
A. Efflux of drug out of the cell by pump, B. Induction of enzyme that hydrolyzes macrolides, C. Methylation of 50s ribsome, D. None of the above
C: Methylation of 50s ribsome
Answer: C: Methylation of 50s ribsome 
Explanation: Methylation of 50s ribosome can lead to cross resistance in macrolides, lincosamides and streptogrammins.