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
Stepwise mutation for drug resistance is seen with: 
Select and explain. 
A. Penicillin, B. Streptomycin, C. Garamycin, D. Kanamycin
A: Penicillin
Answer: A: Penicillin 
Explanation: None