Final answer:
After a high-mass star undergoes a core-collapse supernova, it can become a white dwarf if its core is less than about 1.4 Msun. Cores with a mass between 1.4 and 3 Msun may turn into neutron stars. Cores exceeding 3 Msun are expected to collapse into black holes.
Step-by-step explanation:
When a high-mass star dies by a core-collapse supernova, its fate depends on the mass of its core. If the core has a mass less than about 1.4 times the mass of the Sun (Msun), it can become a white dwarf, composed mainly of helium, carbon, oxygen, or neon, depending on its composition.
For cores with masses between about 1.4 and 3 Msun, they may become neutron stars, which are incredibly dense objects composed primarily of neutrons. Finally, if the mass of the core exceeds approximately 3 Msun, no known force can prevent it from collapsing to an infinitely small volume, becoming a black hole, one of the most mysterious and extreme objects predicted by theory.