The mutation from TTACGCAAG to TTCGCAAG is an example of substitution. In this case, the base "A" has been replaced by "C" in the fourth position of the DNA segment.
- Deletion would involve the loss of a base.
- Insertion would involve the addition of an extra base.
- Inversion would entail the reversal of the order of bases.
Since none of these other options apply, the correct answer is substitution.