Task: Question Answering
Input (English): Question: The proofreading activity of DNA Polymerase: 
 Options:  <1> It is a 5'-3'exonuclease activity. <2> It is a 3'-5'exonuclease activity. <3> It is a 5'-3'polymerizing activity. <4> It is an endonuclease activity. <5> It is a transesterification activity.
Output (English): 2