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
Which one of the components of the TCR (T-cell receptor) is responsible for transmitting signals into the interior of the cell? 
Select and explain. 
A. Zeta chain, B. Alpha chain, C. Beta chain, D. Gamma chain
A: Zeta chain
Answer: A: Zeta chain 
Explanation: The CD3 complex associated with the TCR receptor contains two zeta chains that function for transmitting intracellular signaling.