Answer:
Since there are many factors that can produce a mutation, the event that would be most likely to cause a mutation is a nucleotide is inserted into a DNA strand.
Step-by-step explanation:
A genetic mutation involves an alteration of the DNA that leads to a defect in protein synthesis and a structural or functional alteration of an individual.
Of all the factors that can produce a mutation, the insertion of one or two nucleotides into the DNA strand produces a point mutation, or molecular mutation, of the insertion type.
The other options are not correct because the processes of mRNA traveling out of the nucleus, mRNA releasing from the DNA strand or enzymatic transcription of mRNA in the nucleus can carry over a mutation produced in the DNA, but they are not mutation-producing factors.