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: Pathology
Phagocytosis discovered by- 
Select and explain. 
A. Metchnikoff, B. Ehrlich, C. Ruska, D. Pasteur
A: Metchnikoff
Answer: A: Metchnikoff 
Explanation: None