Question

which type of star will become a black hole when it dies? a protostar a supergiant a white dwarf a red dwarf

Explanation:

A protostar is in the early - formation stage and not dying. A white dwarf is the remnant of a low - to medium - mass star's death. A red dwarf has a very long lifespan and doesn't typically form a black hole. A supergiant, when it dies in a supernova explosion (for very massive supergiants with a core mass above a certain limit, usually more than about 20 times the mass of the Sun), can collapse to form a black hole.

Answer:

a supergiant