In the study of massive stars within the field of physics, which of the following best describes the primary process that leads to the formation of a supernova?
A) Nuclear fusion in the star's core ceases, leading to the collapse of the core and subsequent explosion.
B) The star’s outer layers accumulate a thick atmosphere that prevents the release of stellar winds.
C) The star’s mass decreases significantly, causing it to become a white dwarf without further significant reactions.
D) The star’s core reaches a temperature below the threshold needed for fusion, halting all energy production.