Which of the following best describes why a white dwarf cannot have a mass great

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?
A) 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.
B) 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.
C) White dwarfs are made only from stars that have masses less than the 1.4-solar-mass limit.
D) The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists.