When tempering a new pressing comb, you should:

The process of tempering a new pressing comb is crucial for its effective use in hairstyling, especially with pressed styles that require heat. Heating the comb until it is extremely hot allows the metal to become more flexible while also removing any impurities that may be present from manufacturing. This high temperature prepares the comb for use, ensuring that it conducts heat evenly and efficiently, which is essential for achieving desirable results when styling hair.

While other choices may have some relevance, they do not directly contribute to the tempering process. Submerging the comb in cold water can cause it to warp and is not a method used to prepare a pressing comb. Rubbing oil on the comb might aid in maintenance post-tempering but does not form part of the tempering process itself. Allowing the comb to air dry is unnecessary after heating, as the effective use of a pressing comb relies on its temperature, which is ideally maintained through heating.

Therefore, heating the comb until it is extremely hot is the appropriate action to ensure proper tempering, making it the correct choice for this scenario.