Final answer:
The thermal pressing comb uses its heated upper comb to straighten hair through conduction, where excess electrons from the rubber belt are transferred by contact.
Step-by-step explanation:
The part of the thermal pressing comb that carries the heat and does the pressing is the upper comb. This component of the device is heated and then applied to the hair to straighten it. The process is facilitated by the transmission of heat through conduction, where the upper comb has excess electrons, and these excess electrons are transferred to the comb by contact with the rubber belt.