Which is a frameshift mutation?
a. substitution
b. nonsense
c. silent
d. deletion

I would say D

A frameshift mutation is a mutation caused by an insertion or deletion, which causes a shift in the translational reading frame. ... Instead of just changing one amino acid, frameshifts cause a change in all the amino acids in the rest of the gene

The correct answer will be option-D

Explanation:

A mutation is a change or alteration in the sequence of the DNA of the organism which leads to change the function of the sequence.

The mutation is caused by many mechanisms but one of the mechanism is by adding or deleting the nucleotide in the sequence of the DNA.

The addition or deletion shifts the frame of the DNA while scanning it to form mRNA molecule which then codes a different protein. Therefore the type of mutation is known as "frameshift mutation".

In the given question, since the only deletion is provided therefore, option-D is the correct answer.