Final answer:
A supernova is the correct answer for the remnants of a star seen after implosion and explosion. Quasars, associated with supermassive black holes, emit vast amounts of energy from a small region and are not remnants but active galactic nuclei.
Step-by-step explanation:
The remnants of a star that has undergone both implosion and explosion can result in several different objects, depending on the mass of the star and the dynamics of the process. The correct answer to the remnants observed post such a cataclysmic event is c. a supernova. A supernova is the phenomenon where a massive star explodes, producing a shockwave and leaving behind a neutron star or a black hole. Observations have shown that after the supernova fades, what remains is either a neutron star or, under certain conditions, a black hole. The discovery and study of quasars have significantly contributed to our understanding of black holes. Quasars are active galactic nuclei powered by supermassive black holes and emit enormous amounts of energy from a very small region of space. The energy from quasars is due to matter falling into the accretion disk around the black hole.