Nucleotides are added to the 3' end of a growing DNA chain via nucleophilic attack. In the first step of this reaction:

A. The OH group of the incoming nucleotide attacks the 5' triphosphate of the last nucleotide attached to the DNA strand.
B. The OH group of the incoming nucleotide attacks the 5' monophosphate of the last nucleotide attached to the DNA strand.
C. The OH group of the last nucleotide attached to the DNA strand attacks the 5' triphosphate of the incoming nucleotide.
D. The OH group of the last nucleotide attached to the DNA strand attacks the 5' monophosphate of the incoming nucleotide.