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
Apoptosis activating factor 1 (Apaf-1) 
Select and explain. 
A. Activates caspase 9, B. Activates caspase 8, C. Activates Bcl-1 and Mcl-1, D. Binds with mitochondrial cytochrome C
A: Activates caspase 9
Answer: A: Activates caspase 9 
Explanation: Apaf-1 combines with cytoplasmic cytochrome C that leads to formation of apoptosome complex which further triggers caspase 9 activation. Thus, leading to apoptosis via intrinsic pathway.