DNA ligase does not extend a chain by adding new nucleotides in which manner?

Correct answer: Like a polymerase

DNA polymerase and DNA ligase have different catalytic roles. A polymerase extends a pre-existing primer by adding individual nucleotides, normally to a free 3′ hydroxyl group, so it lengthens a DNA chain. Ligase does not perform that nucleotide-by-nucleotide extension. Instead, it joins already existing DNA ends or seals a nick, using energy to form a phosphodiester bond between neighbouring nucleotides. Consequently, option A correctly describes what ligase does not do. Options B, C, and D describe its actual joining function or the chemical bond produced. The question is about mode of action, not about whether ligase participates in DNA synthesis overall.