The correct answer is (a).
A hydrogen bomb is a thermonuclear weapon that uses the heat from nuclear fission to trigger nuclear fusion. Nuclear fusion is the process of combining two or more atomic nuclei into one larger nucleus, releasing a large amount of energy. Deuterium is a type of hydrogen atom that has one proton and one neutron in its nucleus. When two deuterium nuclei fuse together, they form a helium nucleus and release a large amount of energy.
A nuclear fission bomb, on the other hand, uses the energy released when a heavy nucleus, such as uranium-235, splits into two smaller nuclei. This process is called fission, and it releases a large amount of energy.
(b) is incorrect because thorium is not used in hydrogen bombs.
(c) is incorrect because hydrogen gas is not used in hydrogen bombs.
(d) is incorrect because dynamite and TNT are not used in hydrogen bombs.