The study of the gene is called genetics. Genes are always present in pair form.
The correct answer is DNA.
In DNA, Adenine binds to the thymine and uracil in RNA.
In the question, it has the thymine nitrogenous base.
Hence, we can say that nucleic acid is DNA.
For more information about the DNA, refer to the link:-
https://brainly.com/question/787658