Chargaff's rules of base pairing helped scientists determine how DNA replication occurs. What property of the replication process is explained by Chargaff's rules?

A. The phosphate-sugar backbone of one strand serves as a template for the phosphate- sugar backbone of the complementary strand.

B. The phosphate-sugar backbone of one strand serves as a template for the sequence of four nucleotides in the complementary strand.

C. Adenine (A) and thymine (1) are always paired together within a single DNA strand, as are cytosine (C) and guanine (G).

D. Adenine (A) and thymine (1) always bind to each other across complementary strands, as do cytosine (C) and guanine (G).​