Task: Question Answering
Input (English): Question: The phosphodiester bond: 
 Options:  <1> It is formed by attack from a nitrogenous base to a phosphate. <2> It is formed using NMP as a substrate. <3> In its training PPi is consumed. <4> It involves an alpha phosphate of one nucleotide and an OH group of the ribose of another. <5> It does not need enzymatic catalysis.
Output (English): 4