Which of the Following Best Describes Why a White Dwarf

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4- solar- mass limit?

A) White dwarfs are made only from stars that have masses less than the 1.4- solar- mass limit.
B) Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4- solar- mass limit.
C) The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists.
D) White dwarfs get hotter with increasing mass, and above the 1.4- solar- mass limit they would be so hot that even their electrons would melt.