What can be one benefit of running a restriction-digest gel at a lower voltage?

Correct answer: Better band resolution may be obtained.

In agarose gel electrophoresis, DNA fragments move through the gel under an electric field. A lower, properly controlled voltage generally makes the fragments migrate more slowly, giving them more time to separate according to size. This can reduce band distortion, overheating and excessive smearing, so closely sized restriction fragments may appear as sharper, better-resolved bands. Thus option A is correct. The voltage does not make the restriction enzyme multiply, so option C is biologically impossible. DNA does not instantly burn merely because a gel is run, although excessive voltage can generate heat and damage a sample. Agarose is a polysaccharide gel, not a material that changes into protein, so option D is unrelated.