Final answer:
A supergiant star with a core mass greater than about three times that of the Sun will become a black hole after its collapse at the end of its life.
Step-by-step explanation:
The type of star that will become a black hole when it dies is a supergiant. Specifically, when a star with a core mass greater than about three times that of our Sun (>3 Msun) ends its lifespan, it goes through a colossal collapse. This collapse is so extreme that the dense core's gravity overwhelms all other forces and crushes the core to an infinitely small volume, leaving behind a black hole with such strong gravitational pull that not even light can escape from it. Other types of stars, like those with smaller core masses, end their lives as white dwarfs or neutron stars and do not transform into black holes.
A black hole is formed when a very massive star collapses at the end of its life. When the core of the star has a remaining mass greater than about three times that of the Sun, gravity overwhelms all other forces, causing the core to collapse to an infinitely small volume. This process creates a black hole. Therefore, the type of star that will become a black hole when it dies is a supergiant.