What pairs of bases in DNA are considered complementary?

In DNA, the structure is characterized by specific base pairing that occurs due to the hydrogen bonding between bases. The complementary pairs are adenine (A) with thymine (T) and cytosine (C) with guanine (G). This means that where there is an adenine in one strand of the DNA, there will always be a thymine in the opposing strand, and vice versa for cytosine and guanine.

This base pairing is crucial for the accurate replication of DNA, ensuring that the genetic information is faithfully preserved and transmitted during cell division. The mechanism of these pairs being complementary ensures that the double helix structure is stabilized and promotes the fidelity of genetic coding.

In the context of the given choices, A-T and C-G accurately describe these fundamental pairs, making it clear why this option is the correct choice. It reflects the established and well-supported understanding of DNA structure in molecular biology.