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.
Q: Question: The MIC-A protein, expressed in various cell types and induced by cellular stress situations, is recognized by:
Options: <0> KIR receivers. <1> The Major Histocompatibility Complex (MHC). <2> The NKG2D receptor. <3> B lymphocytes <4> NOD type receivers.
A:
pharmacology