Which is an example of a substitution mutation?

CAG - TTA - CAC mutates to CAG - GAC - TTA - CAC
CAG - TTA - CAC mutates to CAG - TTA - CAC - AT
CAT - GGC - TAC mutates to CAT - GGC - TAG
CAT - GGC - TAC mutates to ATG - GCT - AC

CAT - GGC - TAC mutates to CAT - GGC - TAG

Explanation:

Changes occur in the nucleotide sequence of the DNA molecule. These changes referred to as MUTATION are usually due mistakes during DNA replication or induced by mutagens (mutation-causing substances). Mutation can be of different types depending on the kind of change that occured to the nucleotide sequence. Based on this question, one of the mutation types is SUBSTITUTION MUTATION.

Substitution mutation is a kind of mutation in which one or more nucleotide base replaces another in the sequence.

The option that suits an example of substitution mutation is: CAT - GGC - TAC mutates to CAT - GGC - TAG because Guanine nucleotide replaces Cytosine nucleotide in the third CODON i.e. TAC becomes TAG.

the correct answer is:

a population changes in response to a change in the environment.