Instructions: In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
Input: Question: Among the characteristic components of the adaptive immune system are: 
 Options:  <0> The epithelial cells. <1> The macrophages. <2> The NK lymphocytes. <3> C-reactive protein <4> The B lymphocytes
Output:
biology