What type of bond is formed by complementary base pairing in DNA?

Complementary base pairing in DNA involves the formation of hydrogen bonds between the bases of the two strands of the DNA molecule. Each specific base pairs with another: adenine pairs with thymine, which forms two hydrogen bonds, while guanine pairs with cytosine, which forms three hydrogen bonds. This hydrogen bonding is crucial because it provides the necessary stability to the double helix structure of DNA while still allowing the strands to separate for processes like replication and transcription.

Covalent bonds, on the other hand, are the type of bonds that link the sugar and phosphate backbone of the DNA strand, but they do not play a role in the specific pairing of the bases. Ionic bonds typically involve the electrostatic attraction between charged ions, which is not relevant to the pairing of bases in DNA. Dative bonds, or coordinate bonds, involve a pair of electrons being shared between atoms, again unrelated to the base pairing mechanism in DNA. Therefore, the hydrogen bonds are essential for maintaining the complementary pairing of bases, making them the correct answer.