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: Microbiology
Diphtheria is pathogenic only when infected with 
Select and explain. 
A. Beta phage, B. Alfa phage, C. Lambda k12, D. Delta phage
A: Beta phage
Answer: A: Beta phage 
Explanation: None