Task: Question Answering
Input (English): Question: Relating to topoisomerases: 
 Options:  <1> They are enzymes that convert the D-amino acids into L-amino acids. <2> They are enzymes that synthesize DNA. <3> They are enzymes that participate in the union of the subunits of the ribosome. <4> They are enzymes that denature DNA. <5> DNA gyrase is a special toposiomerase.
Output (English): 5