Task: Question Answering
Input (English): Question: Determines the isotype change of the immunoglobulin heavy chain: 
 Options:  <1> The receptor of cell B. <2> The CD40 molecule and the cytokines. <3> IgM or IgD of the lymphocyte membrane. <4> Age. <5> The location of the lymphocyte within the germinal center.
Output (English): 2