Anova is a sudden brightening of a star that occurs when
a) material is transferred onto the surface of a white dwarf from a companion star in a binary system, then subsequently blasted into space by a runaway thermonuclear explosion (leaving the white dwarf intact to repeat the process).
b) 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.
c) the electron degenerate iron core of a massive star collapses after its mass becomes greater than the chandrasekhar mass limit.
d) material is transferred onto a neutron star from a companion star in a binary system, causing the neutron star to collapse into a black hole.