The correct possible sequence in the life cycle of a massive star is:
**nebula, protostar, star, super red giant, supernova, neutron star.**
In this sequence:
1. A nebula (cloud of gas and dust) collapses under its gravity to form a protostar.
2. The protostar becomes a main sequence star.
3. The star evolves into a super red giant.
4. The super red giant undergoes a supernova explosion.
5. Depending on the mass, the remnant can either become a neutron star or a black hole.
This sequence accurately represents the life cycle of a massive star.