In Earth's Solar System,a Nebula Is Believed to Have Formed

In Earth's solar system,a nebula is believed to have formed around the early Sun.Planetesimals gradually coalesced out of this nebula and accreted to form the planets-a process requiring a total of about 100 million years.How would you describe the Sun at the end of this process?

A) The Sun was about halfway through its protostar phase.
B) The Sun had just become a pre-main-sequence star.
C) The Sun was at the end of its existence as a pre-main-sequence star.
D) The Sun had ended its pre-main-sequence phase and had become a main-sequence star.