Final answer:
A Red giant is not a stage a star can become after it dies; it is instead a phase before the star's death. Stars can become white dwarfs, neutron stars, or black holes after they have exhausted their fuel, depending on their initial mass.
Step-by-step explanation:
The answer to the question 'Which of the following is NOT something a star can become after it dies?' is c) Red giant. Stars undergo various transformations after they deplete their nuclear fuel. Stars with core masses less than 1.4 times that of the Sun's mass (Msun) eventually cool down and become white dwarfs. As they radiate away their heat over many billions of years, they may end up as black dwarfs, cold stellar corpses.
Stars with core masses between 1.4 and about 3 Msun generally collapse into neutron stars. In some cases, these neutron stars can be observed as pulsars. If a star has a core mass greater than about 3 Msun, it is theorized that such a core will collapse under gravity to form a black hole. However, a Red giant is a stage that some stars pass through before their final death, not a stage after death.