Question

what do we call stars with low surface temperature and high luminosity?
main sequence
red supergiants
white dwarfs
blue giants

Explanation:

Red supergiants have large radii. Despite their low surface - temperatures, their large size gives them high luminosities. Main - sequence stars have a range of temperatures and luminosities related to their mass. White dwarfs are small and hot. Blue giants are hot and luminous.

Answer:

red supergiants