Correct Answer:
A. Red giant
When a star exhausts its hydrogen fuel in the core, it begins to contract, causing its core temperature and pressure to rise. This allows helium fusion to begin, converting helium into carbon. During this phase, the star's outer layers expand significantly and cool, causing it to become a Red Giant. This is a crucial stage in the evolution of low-to-intermediate mass stars like our Sun.
- A White Dwarf is the dense, hot remnant of a star after it has shed its outer layers.
- A Neutron Star is the extremely dense core left after a massive star undergoes a supernova.
- A Supernova is a powerful and luminous stellar explosion, marking the end of a massive star's life.