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: What is a prodrug?
Options: <0> A drug of series of a therapeutic class. <1> A drug that has been withdrawn from the market. <2> An inactive product that is enzymatically converted to an active drug. <3> A compound of natural origin from which one or more drugs are obtained by hemisynthesis. <4> A drug that lacks activity but enhances the action of others.
A:
medicine