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
The presence of which of the following factors in
viruses makes protective vaccines a possibility? 
Select and explain. 
A. Enzymes, B. Protein coat, C. Polysaccharide, D. Lipids
B: Protein coat
Answer: B: Protein coat 
Explanation: None