Question

which statement about stars is correct? white dwarfs become main - sequence stars when they gain mass. star formation begins in a nebula. main - sequence stars are formed by comets. supergiants are stars that can absorb black holes.

Explanation:

• White dwarfs are the remnants of stars that have exhausted their nuclear fuel. They do not become main - sequence stars again when they gain mass.
• Main - sequence stars are formed from the gravitational collapse of a nebula, not from comets.
• Supergiants are very large and luminous stars, but they cannot absorb black holes. Black holes have extremely strong gravitational fields, and it is the black hole that can potentially affect the supergiant (e.g., in a binary system where the black hole can accrete matter from the supergiant), not the other way around.
• Star formation begins in a nebula. A nebula is a cloud of gas and dust in space. When a region within a nebula becomes dense enough, gravitational collapse occurs, leading to the formation of a protostar, which then evolves into a main - sequence star.

Answer:

Star formation begins in a nebula.