At the end of its evolution, a star can become:
- a white dwarf
- a black hole
- a neutron star
So the correct answers are: a white dwarf, a black hole, and a neutron star.
A brown dwarf is not the end state of a star but rather an object that did not reach the necessary mass to ignite nuclear fusion in its core, and a supernova is an explosive event in the life cycle of a massive star, not a final state.