Answer:
a) white dwarf
Explanation:
A small to average mass star usually end up as white dwarfs. Once the fuel is used up, the nuclear fusion reaction stops in the core of the star. It starts expanding and forms a red-giant. Majority of the mass is thrown before the star collapses to a small core known as white dwarf.
Thus, a star having 0.5 solar mass would eventually end up as a white dwarf.
