You will be given a definition of a task first, then some input of the task.
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: What is the PCNA or nuclear cell proliferation antigen?
Options: <1> It is a protein that prevents the double helix from forming in the replication bubble. <2> It is a protein that increases the ability to replicate long fragments of eukaryotic DNA polymerase. <3> It is the protein responsible for the elimination of positive superhelices. <4> It is the typical conformation of the DNA double helix in eukaryotes. <5> It is the enzyme responsible for copying the DNA of the telomeres.
Output:
2