PLZ HELP
which is a possible sequence in the life cycle of a massive star
supernova, star, black hole, planetary nebula, super red giant, protostar
super red giant, protostar, nebula, star, neutron star, supernova
planetary nebula, super red giant, protostar, supernova, star, black hole
nebula, protostar, star, super red giant, supernova, neutron star