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
Pocks on chick embryo are formed by all except - 
Select and explain. 
A. Variola, B. Vaccinia, C. Chickenpox, D. Cowpox
C: Chickenpox
Answer: C: Chickenpox 
Explanation: None