Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: In the process of maturation of the affinity of the B lymphocytes in the germinal centers, they act as accessory cells: 
 Options:  <1> Macrophages <2> Th1 lymphocytes. <3> Mastocytes <4> Follicular dendritic cells. <5> Langerhans cells.
