Answer:
Protostar
Step-by-step explanation:
Protostar is a contracting mass of gas that depicts an early stage in the formation of a star, before nucleosynthesis has started. On the other hand, a nebula refers to a large cloud of contracting gas spread out in an extremely large volume.
Thus, stars initiate as part of nebulas. When the contracting gas and dust from a nebula becomes so dense and hot, nuclear fusion starts and a star is born.