Final answer:
True, all elements other than hydrogen are created by nuclear fusion in stars or during supernovae, with heavier elements than iron produced in the extreme conditions of a supernova.
Step-by-step explanation:
The statement that all elements other than hydrogen are produced during nuclear fusion in the core of stars or during a supernova is true. The majority of elements in the universe are created through the process of nuclear fusion within stars. In the incredibly hot and dense core of a star, hydrogen nuclei fuse to form helium, and through a series of more complex reactions, heavier elements up to iron can also be synthesized. When a massive star exhausts its nuclear fuel, it may undergo a supernova explosion. During this violent event, extreme temperatures and pressures cause the synthesis of elements heavier than iron. These newly formed elements are then dispersed into space, contributing to the cosmic abundance of elements that we observe.