Which enzyme is primarily responsible for degrading single-stranded DNA from either end?

The correct choice is Exonuclease VII, which is primarily responsible for degrading single-stranded DNA from either end. This enzyme functions as a 5' to 3' and 3' to 5' exonuclease, allowing it to efficiently remove nucleotides from both ends of single-stranded DNA molecules. Such versatility makes it an important tool in molecular biology for processes requiring the degradation of single-stranded DNA.

In contrast, Exonuclease I is specific for degrading single-stranded DNA but operates only from the 3' end, while Exonuclease III primarily degrades double-stranded DNA in the 3' to 5' direction. S1 nuclease also acts on single-stranded DNA, but it does so by cleaving internucleotide phosphodiester bonds and is more specialized in its action compared to Exonuclease VII. Thus, Exonuclease VII stands out for its ability to degrade single-stranded DNA from both ends, making it the answer in this context.