Given the task definition and input, reply with output. 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: Infections caused by Clostridium tetani, Bordetella pertussis, Corynebacterium diphtheriae and Vibrio cholerae have in common:
Options: <0> The type of transmission. <1> The reservoir. <2> The production of exotoxins. <3> The affected organs. <4> The route of infection.
biology