Final answer:
Adenine and uracil is NOT a base pair found in a nucleic acid.
Step-by-step explanation:
The base pair that is NOT found in a nucleic acid is adenine and uracil. Adenine and uracil are found in RNA, but not in DNA. The other base pairs mentioned in the options, such as adenine and guanine, thymine and adenine, and cytosine and guanine, are all found in both DNA and RNA.
Learn more about Base pairs in nucleic acids