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
Complement attaches to immunoglobulin at ? 
Select and explain. 
A. Aminoterminal, B. Fab region, C. Variable region, D. Fc fragment
D: Fc fragment
Answer: D: Fc fragment 
Explanation: Ans. is 'd' i.e., Fc fragment . Fc fragment is composed of the carboxyterminal. It determines the biological activity such as complement fixation, placental transfer, skin fixation and catabolic rate. CH-2 of Ig G and CH, of IgM bind to C1q poion of CI.