Answer:
D. A nitrogen base has been added to the DNA molecule.
Explanation:
You can see that the sequence for the nitrogen bases are in the exact same order after the exposure, this rules out A. You can count how many bases there are, 7 before and 8 after so it cannot be B. Lastly, given that they are in the same order as were before and that a base has been added, you can see that no bases were replaced (so not C) and that D is your answer.
Answer:
For a second there I thought it was a dog
