An extra larger band appears in a sample. What may it indicate?

Correct answer: Incomplete digestion

Restriction enzymes cut DNA at particular recognition sites. If digestion is complete, the molecules are cut wherever the relevant sites are present, producing the expected smaller fragments. If some DNA molecules are not cut at all sites, partly cut or uncut molecules remain larger than the expected fragments.

On a gel, these incompletely digested molecules can appear as an additional band of larger size, often alongside the normal digestion bands. Thus an extra larger band may indicate incomplete digestion, making option A the best answer. It does not indicate complete DNA loss, chlorophyll synthesis, or translation alone, because those processes do not explain the presence of an unexpectedly large DNA fragment in a restriction-digestion sample.