In a Type Ia Supernova, the Cause of the Violent

In a Type Ia supernova, the cause of the violent outburst is:

A) the sudden emission of a shell of stellar material from a dying low-mass star
B) the collapse of a very massive protostar to the main sequence
C) an enormous release of neutrinos during a sudden episode of hydrogen fusion
D) the transfer of so much mass from a companion star that a white dwarf goes "over the limit" and collapses, causing an enormous amount of sudden fusion
E) two neutron stars colliding with each other