According to the stringent rules of complementary base pairing in the Watson-Crick DNA double helix, — Biomolecules Chemistry Question

💡 Solution & Explanation

Complementary base pairing requires a purine to pair with a pyrimidine. Adenine strictly pairs with Thymine utilizing 2 hydrogen bonds ($A=T$), and Guanine pairs with Cytosine utilizing 3 hydrogen bonds ($G\equiv C$).