Given the task definition and input, reply with output. In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: The systematic nomenclature rules of the IUPAC give priority as a main function, from among the following functional groups, to:
Options: <1> Amines <2> Carboxylic acids. <3> Nitriles <4> Carboxylic ethers. <5> Aldehydes.
2