Please help with my biology

Substitution

Explanation:

Deletion would be deleting (C)

Insertion would be inserting another letter

C. Substitution

Explanation:

Mutations occur when a gene sequence is changed in one way or another. In this case, the 6th base, C, was swapped with an A. This is a substitution mutation where one base is substituted for another. An easy way to tell this is substitution is that the number of bases does not change in the mutated sequence.