Which option is correct about ligase and DNA repair?

Correct answer: Ligase can seal a break or nick in a DNA strand

DNA repair often leaves a nick or discontinuity in the sugar-phosphate backbone after damaged portions have been removed and the correct nucleotides have been inserted. DNA ligase seals this remaining break by catalysing formation of the missing phosphodiester bond, thereby restoring continuity of the strand. Hence option A is correct. Ligase does not generally destroy DNA, so B reverses its actual role. It is not a protein-staining reagent, making C irrelevant, and although water is present in biological reactions, D is scientifically meaningless because ligase requires appropriate substrates, ions, pH, and energy conditions rather than water alone.