The initial mechanism for repairing nucleotide errors in dna is
mismatch repair
dna polymerase proofreading
nucleotide excision repair
thymine dimers

DNA polymerase proofreading

Explanation:

DNA polymerase is the main enzyme responsible for the DNA replication process. In addition to this function, DNA polymerase has the function of repairing possible nucleotide errors in newly replicated DNA, in a process called proofreading.

The proofreading activity that DNA polymerase performs prior to the addition of a new nucleotide is mandatory. If there is no binding to review, DNA polymerase cannot do polymerization either. There must always be some nucleotides already linked together and paired with the template, so that DNA polymerase can act. This small new patch, paired with the template strip, provides the free 3'-OH end so that DNA polymerase can add the next nucleotide.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

i think the answer is b.