Task: Question Answering
Input (English): 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 (English): 2