What process repairs damage to a preexisting double helix?

The correct answer is nucleotide excision repair.

Explanation:

The nucleotide excision repair process occurs to repair the damage found in the DNA, and occurs in both prokaryotic and eukaryotic cells.

During this process, anything that is abnormal for the DNA is identified, and once identified, it is repaired or removed.

It is identified as damage to everything that destabilizes the double helix within the normal behavior of DNA.