Answer: The correct answer is -
D) Double Helix.
Step-by-step explanation:
DNA strands are unzipped to form new complimentary strands in the process of DNA replication.
DNA replication is a process of producing two molecules of DNA from a single DNA molecule, which is double stranded or having double helix structure.
During this process, the two strands of original DNA molecule are initially unzipped so that they act like template strands.
Using the template strand, enzyme DNA polymerase adds dNTP (deoxyribonucleoside triphosphate, which is monomer of DNA) in the direction 5' to 3', which is antiparallel to the direction of template strands.
Thus, DNA strands are unzipped at the point of double helix so as to expose the template strands.