What is the benefit of cleanup after restriction digestion?

Correct answer: Removing enzyme, buffer salts, and small fragments

The governing concept is purification of a DNA sample before a downstream molecular-biology reaction. Restriction digestion mixtures contain the desired DNA fragments together with enzyme, buffer components, salts, and sometimes very small unwanted fragments. Cleanup removes or reduces these contaminants, improving DNA purity and making later steps such as ligation, cloning, or amplification more reliable. Option A is correct because it describes the practical purpose of the cleanup. Cleanup is intended to preserve and recover useful DNA, not destroy it. It does not synthesize protein, and staining agar is a separate gel-visualization operation unrelated to purification of the digestion mixture.