Answer B
From least luminous to most luminous:
White dwarf A star - White dwarfs are small, dense, and dim stars that have exhausted their nuclear fuel and have cooled down. They emit very little light, and their luminosity is much lower than that of most other types of stars.
Red giant K star - Red giants are large and relatively cool stars that have exhausted the hydrogen fuel in their cores and have expanded to several times their original size. They are brighter than main-sequence stars like our Sun but less bright than supergiants.
Supergiant F star - Supergiants are massive and luminous stars that are in the last stages of their lives. They are much larger and brighter than most other types of stars, including red giants, and have a high luminosity. F-type supergiants are particularly bright and have a high surface temperature.