The correct option is B a few nucleotides (not in multiples of three) get inserted or deleted
As the name indicates, frameshift mutations are those that result in a shift in the reading frame of the nucleotide sequence. Since a codon is made of three nucleotide bases, an insertion or deletion of three (or multiples of three) nucleotide bases would not result in a shift in the reading frame; it would rather result in extra codon(s) or missing codon(s) respectively. This eventually leads to a modified protein (due to missing or additional codons). Thus, they may be called non-frameshift mutations. However, if the number of nucleotide bases inserted or deleted is not a multiple of three, it would alter the reading frame and hence can be called frameshift mutations. For example: The muscular dystrophy is caused due to a frameshift mutation which leads to the weakness of muscles.