What is the function of the enzyme topoisomerase in DNA replication?

• A. Relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix.
• B. Elongating new DNA at a replication fork by adding nucleotides to the existing chain.
• C. Reattaching the hydrogen bonds between the base pairs in the double helix.
• D. Building RNA primers using the parental DNA strand as a template.