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: Ethidium bromide is a molecule that has a very low fluorescence yield in solution. However, its quantum yield increases remarkably when:
Options: <1> It is atomized. <2> It is interspersed between consecutive base pairs of the DNA double helix. <3> The aqueous solution containing it is oxygenated. <4> It binds to a heavy metal forming a complex. <5> It is oxidized by the action of the enzyme glucoxaoxidase.
Output:
2