A Nova Is a Sudden Brightening of a Star That

Multiple Choice

A nova is a sudden brightening of a star that occurs when

A) material from a companion star is transferred onto the surface of a white dwarf in a binary system and is subsequently blasted into space by a runaway thermonuclear explosion,leaving the white dwarf intact to repeat the process.
B) the electron-degenerate iron core of a massive star collapses after its mass becomes larger than the Chandrasekhar mass limit.
C) material from a companion star is transferred onto a neutron star in a binary system,causing the neutron star to collapse into a black hole.
D) material from a companion star is transferred onto the surface of a white-dwarf star in a binary system,after which runaway carbon fusion reactions cause the entire white dwarf to be destroyed in an explosion.