Final answer:
The first step of PCR, denaturation, is optimally performed at 94°C, which is the correct temperature to separate the double-stranded DNA.
Step-by-step explanation:
An appropriate temperature for the first step of PCR (Polymerase Chain Reaction) is s94°C. Thi step is known as the denaturation step, where the double-stranded DNA is heated to separate it into two single strands, allowing the primers to bind in the subsequent annealing step.
Each of these steps within a PCR cycle requires a specific temperature: denaturation at around 95°C, annealing of primers usually around 55°C, and extension by the polymerase at 68-72°C.