Mutation is the word for a change in a sequence of DNA. It can be either a single point mutation (changing only a single nucleotide base) or it can affect a larger segment of DNA (or delete a segment of DNA entirely). Since the nucleotide base sequence in DNA encodes for protein biosynthesis, any change in the DNA sequence has the possibility to chain the amino acid sequence of a protein polypeptide chain. If the mutation is small enough, it can still encode for the same amino acid or perhaps a very similar one chemically. Also, the change could be in a part of the protein that is not important to folding or structure. But if the change is large enough or in an important part of the protein then the protein can lose its funtionality. An example of this is sickle cell anemia. So the severity of the mutation can vary widely, but the best answer to the question is C, the production of a different version of a protein.