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
Which of the following is primary cell line ? 
Select and explain. 
A. Chick embryo fibroblast, B. Hela cells, C. Vero cells, D. WI-38
A: Chick embryo fibroblast
Answer: A: Chick embryo fibroblast 
Explanation: Ans. is 'a' i.e., Chick embryo fibroblast Chick embryo fibroblast is primary cell culture.