Use the HR diagram below to answer the question. Labeled HR diagram. The main sequence slopes from the upper-left of the diagram, which is blue, to the bottom-left of the diagram, which is red-orange. White dwarfs cluster at the bottom of the diagram, in the light blue section. Red supergiants cluster at the top of the diagram, in the orange-red section.

Which of the following types of stars is the least bright?

Blue main sequence
Red giant
White dwarf
Yellow main sequence