The correct option is C white dwarf
A red giant star is the later stage of a star whose mass is less than or equal to about 8 times the Sun's mass. Such stars including our Sun, swell into a massive red giant star. The giant star then explodes and releases almost of all its contents in the form of a very hot, dense, and ionised gaseous matter called a planetary nebula. The extremely dense core of the star is left behind, and is called a white dwarf, because it shines bright white and looks as small as the Moon.