Which type of mutation is most likely to result in a non-functional protein?

A nonsense mutation is most likely to result in a non-functional protein because it introduces a premature stop codon into the sequence of a gene. This change causes translation to halt before the entire protein is synthesized, leading to a truncated protein that is often non-functional. The premature termination disrupts the protein's structure and function, which may severely impair its role in the organism's biological processes.

In contrast, beneficial mutations can enhance protein function, neutral mutations typically do not affect the protein’s function, and silent mutations do not alter the amino acid sequence of the protein at all. Therefore, they are unlikely to lead to a non-functional protein since the overall sequence remains unchanged. The specificity of nonsense mutations makes them particularly impactful in disrupting protein synthesis, which is why they are the correct choice in this context.