Answer:
DNA is also called deoxyribonucleic acid which is made up of two chains which wind around each other to form a double helix model. The 2 DNA strands are also called polynucleotides and they are made up of monomeric units known as nucleotides. These nucleotides are made up of one of four nitrogen-containing nucleobases: cytosine, guanine, adenine and thymine, a phosphate group, and sugar known as deoxyribose.
Nitrogen bases present on the two separate polynucleotides strands are bound together with the help of base pairing (such as adenine with Thymine) and with hydrogen bonds to form double-stranded DNA.
So, adenine in DNA is complementary to thymine.