Answer:
B. insertion
Step-by-step explanation:
It can be observed that nitrogenous bases were added to the codon sequence, this is a characteristic of gene insertion mutations.
Insertion is the addition of base pairs to the DNA sequence.
This type of mutation occurs very common when replicating the DNA intron regions where large repetitive sequences (microsatellite regions) are present.
Insertions may occur due to uneven crossings during meiosis.