A Main-Sequence Star Begins Its Life with a Certain Amount

A main-sequence star begins its life with a certain amount of mass, but it eventually evolves into a giant star hundreds of times as large as it was when it was on the main sequence. How is this possible?

A) Nuclear reactions result in additional mass.
B) Stellar evolution involves mergers of stars-and that provides the additional mass needed for expansion.
C) Additional mass is not needed. As the star expands its density decreases.
D) Stars are constantly being bombarded by dust, as are the planets; this provides the additional mass needed for expansion.