Answer:
D) substitution.
Step-by-step explanation:
Substitution mutations are those in which one base pair is replaced by another base pair; they are called transition when substitution occurs between bases of the same class, purine to purine (A - G) and pyrimidine to pyrimidine (T - C); and transverse, when the substitution is between bases of different class, purine for pyrimidine and pyrimidine for purine.