The correct answer is b) missense mutation.
A missense mutation is a point mutation that results in the substitution of one amino acid for another in the protein encoded by the gene. This occurs because of a change in a single nucleotide in the DNA sequence, which leads to a different codon that specifies a different amino acid. Unlike a nonsense mutation, which creates a premature stop codon and results in a truncated protein, or a frameshift mutation, which alters the reading frame and usually results in a completely different and nonfunctional protein, a missense mutation may have little to no impact on the protein’s function, or it could have significant effects, depending on the properties of the substituted amino acid.