Which is the correct base pairing found in a normal DNA molecule?

In a normal DNA molecule, Adenine (A) pairs with Thymine (T) through two hydrogen bonds, while Guanine (G) pairs with Cytosine (C) through three hydrogen bonds. This is known as Chargaff's rule or complementary base pairing. Adenine and Guanine are purines (with double-ring structures), while Thymine and Cytosine are pyrimidines (with single-ring structures). A purine always pairs with a pyrimidine to maintain a uniform width of the DNA double helix. This complementary base pairing is fundamental to DNA's structure as proposed by Watson and Crick, and ensures accurate DNA replication and transcription.