Final answer:
The energy required to initiate the fusion process in a thermonuclear bomb is provided by a fission reaction within the hydrogen bomb that creates the necessary high temperatures for fusion.
Step-by-step explanation:
The energy required to start the fusion process in a thermonuclear bomb is provided by a fission reaction. In a thermonuclear weapon, such as a hydrogen bomb, a nuclear fission bomb is used as a trigger. This fission bomb, when detonated, releases a tremendous amount of energy, which produces the extremely high temperatures (about 15,000,000 K or more) necessary for nuclear fusion to occur. At these temperatures, all molecules dissociate into atoms, and the atoms ionize, creating a plasma state where fusion can happen.