A mutation is defined as:
O A change in the DNA sequence.
Anything that changes in an an embryo.
Any change in the physical features of a human.

Option A) A change in the DNA sequence.

Explanation:

Mutation is the change in the base sequence of DNA nucleotides. For example: if the codon GAG is change to GAC, you will say that mutation have caused the third nitrogenous base, guanine to become Cytosine.

Thus, mutation brings about a change in DNA sequence