In the listed life cycle, which stage comes immediately after nebula?

• A. Sun-like star
• B. Red giant
• C. White dwarf
• D. Black dwarf

Answer: (A)

A star begins life as a nebula, a cloud of gas and dust, which collapses under gravity to form a protostar that then becomes a Sun-like star when hydrogen fusion starts in its core. That Sun-like star is the next stage after the nebula in the typical life cycle, because it represents the stable, hydrogen-burning phase the star enters before it evolves further. After this stage, the star would later become a red giant, then a white dwarf, and finally, over an immense timescale, a black dwarf. The other options are stages that occur later in the sequence.