quasar protostar red giant white dwarf
I gave my students this multiple choice question: After a star runs out of most of its hydrogen fuel, it becomes hotter and more luminous. What stage does this represent in the life cycle of a star?

Only one answer is correct among these 4 choices:
- quasar
- protostar
- red giant
- white dwarf

Could you tell me which one is correct?

red giant