How have scientists proved that supernova explosions occur?

a. bursts of gamma rays are given off during supernova explosions that can be detected by special instruments

b. ultraviolet rays produced when a supernova explodes are detected on earth using special sensors

c. photons of light travel to earth, allowing astronomers to see the explosion through a telescope

d. infrared rays emitted by a supernova explosion allow scientist to create a thermogram of the event