Answer: Hydrogen bomb uses the process of nuclear fusion reactions.
Explanation: Nuclear fusion reactions are the reactions in which two lighter nuclei fuse together to form a heavier nuclei.
Hydrogen bomb uses the fusion of isotopes of hydrogen. These reactions require a large amount of heat to be initiated.
Reaction for the hydrogen bomb are:
Step 1 :

Step 2:

Step 3:

Overall reaction:

The hydrogen bomb is also known as Thermonuclear bomb.