Question

what is the sun classified as on the hertzsprung - russell diagram?
red giant
supergiant
white dwarf
main sequence star

Explanation:

The Hertzsprung - Russell (H - R) diagram plots stars' luminosity against their temperature (or spectral type). Main - sequence stars, like the Sun, are in the stage of fusing hydrogen into helium in their cores. Red giants are larger, cooler, and more luminous stars that have exhausted hydrogen in their cores. Supergiants are extremely large and luminous. White dwarfs are small, hot, and dim, remnants of stars that have shed their outer layers.

Answer:

main sequence star