Final answer:
The enzyme that catalyzes the formation of transient double-stranded breaks ahead of the replication fork to relieve supercoiling is DNA gyrase (option b).
Step-by-step explanation:
The enzyme that catalyzes the formation of the transient double-stranded breaks ahead of the replication fork, relieving supercoiling during DNA replication, is DNA gyrase (option b).
Helicase separates the DNA strands at the origin of replication, while topoisomerase breaks and reforms DNA's phosphate backbone ahead of the replication fork to relieve the pressure caused by supercoiling. This allows the replication machinery to proceed smoothly.
On the other hand, DNA ligases are responsible for joining the ends of DNA fragments, and DNA polymerases are responsible for synthesizing new DNA strands from the existing template strands.