Q: 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.
Question: It has superficial cells with abundant glycogen: 
 Options:  <0> Language. <1> Esophagus. <2> Thin skin <3> Vagina. <4> Thick skin.
A:
biology