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: On a blood agar plate, a greenish or brown halo around a bacterial colony indicates that the bacteria produces: 
 Options:  <0> A siderophore. <1> α hemolysis. <2> Coagulase <3> β galactosidase. <4> Neutral metabolites
A:
biology