Insertion is a type of mutation that consist in the addition of one or more nucleotides into a genetic sequence. This type of mutation occurs in nature, particularly by viruses that insert its genetic material into its host and by bacteria that uses plasmids to transfer desired traits. In this example scientists copied the insertion mutation approach to transform bacteria with a modified plasmid, producing recombinant bacterial cells with the desired plasmid inserted into its genetic sequence.
The answer is C. Insertion. The question asks for a mutation; insertion is a frameshift mutation. Crossing over is not a mutation because it occurs during meiosis when the chromosomes trade information!! ;)
