Final answer:
The correct answer is d) Nuclei. At 15 million degrees, nuclei can overcome the electrical potential barrier and fuse, leading to the birth of a star. This process is called the proton-proton chain and results in the formation of helium and the release of energy.
Step-by-step explanation:
At 15 million degrees, nuclei begin to fuse together and a star is born. The correct answer is d) Nuclei. In such extreme conditions, the protons in the core of a stellar object are moving at such speeds that they can overcome the electrical potential barrier that normally keeps them apart.
These protons, which are the nuclei of hydrogen atoms, can then get close enough for the strong nuclear force to cause them to fuse into helium through a process known as the proton-proton chain. During this fusion process, four protons come together, and two of them convert into neutrons, resulting in a helium nucleus and the release of energy in the form of photons or light energy. This nuclear fusion is the process that powers stars and allows them to shine.