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
Which of the following complement component can be activated in both common as well as alternative pathways? 
Select and explain. 
A. C1, B. C2, C. C3, D. C4
C: C3
Answer: C: C3 
Explanation: The complement proteins can be activated by 3 pathways; classical, lectin and alternate pathways. Terminal pathway is common to the first three pathways and is present at the level of post activation stage of C3. It eventually leads to the membrane attack complex that lyses cells. C3 is the first common complement protein to be activated in both classical and alternate pathway.