Task: Question Answering
Input (English): Question: Which of the following answers is true about the HLA molecules? 
 Options:  <1> They are very polymorphic nuclear proteins. <2> They are divided into molecules of class IgG, IgA and IgM. <3> They join peptides and present them on the cell surface. <4> They interact with cytokines to modulate the immune response. <5> They are monomorphic.
Output (English): 3