Answer: D. Frameshift mutation
Step-by-step explanation:
A nonsense mutation is one in which a codon codifying for an amino acid is replaced by a stop codon, resulting in a premature end to translation (e.g. TAT [Tyrosine] >> TAG [stop]).
A missense mutation is one in which a codon is altered in such a way that it ends up codifying for a different amino acid (e.g. AUA [Isoleucine] >> AUG [Methionine]).
A point mutation is any mutation which involves the altering of a single nucleotide (such as the examples given above), regardless of its effect on the resulting protein.
Finally: a frameshift mutation is one which alters the reading frame of a gene, which results in a whole different set of nucleotides being treated as individual codons by the translation machinery. The consequence of this is a significant change in the resulting amino acid sequence. Frameshift mutations may be the result of several mechanisms which include insertions and deletions. The example given in the picture appears to show an example of one such mutation.