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: Pharmacology
Filgrastim is a : 
Select and explain. 
A. T–cell stimulating factor, B. GnRH analogue, C. G–CSF, D. GM–CSF
C: G–CSF
Answer: C: G–CSF 
Explanation: None