The correct answer is DNA helicase.
DNA helicases help in the unwinding of DNA. They play an essential function at the time of DNA replication as they distinct the double-stranded DNA into single strands, and permit each strand to undergo copying or duplication.
It works by melting the hydrogen bonds, which holds the DNA into the double helical composition. The region of the DNA where the DNA helicase has unzipped the DNA is called replication fork.