Which of the following is not part of a star?
a. photosphere
b. corona
c. radiative zone
d. dark spot

Answer;

D. Dark spot

Explanation;The parts of a star includes the core, radiative and convective zones, photosphere, chromosphere and corona.Corona is the outermost part of the star that extends for million miles into the space.Photosphere is a part of the star outside the stellar zones, where visible light is emitted.Radiative zone is a layer of the star outside the core where energy is transported by radiation. Chromosphere is a layer outside photosphere. In the sun this layer is red colored from an abundance of hydrogen gas.Therefore, in our question, Dark matter is not a layer or a part of a star.