Task: Question Answering
Input (English): Question: The T lymphocyte receptor (TCR): 
 Options:  <1> Experience change of class. <2> Does not experience affinity maturation. <3> It transmits signals to the T lymphocyte on its own. <4> It has two sites of antigen recognition such as antibodies. <5> Performs effector functions mediated by its constant regions.
Output (English): 2