When DNA replication begins, ____.

A) the two DNA strands unwind from each other
B) the two DNA strands condense
C) two DNA molecules bond
D) old DNA strands move to pair with new strands
E) the sugar-phosphate backbone is degraded

During DNA replication, the two strands of DNA unwind from each other, allowing each strand to serve as a template for the synthesis of a new complementary strand. This process is carried out by enzymes called DNA polymerases, which use the single-stranded template to add nucleotides to the new strand in a complementary fashion. As the nucleotides are added, they are joined together by the formation of covalent bonds between the sugar and phosphate groups, forming the sugar-phosphate backbone of the new strand.