Which spectral class would the Sun likely move into upon becoming a red giant?

Answer

K or M spectral classes

The transition to a red giant places the star into the K or M spectral classes, which are fundamentally cooler classes compared to the G class the Sun occupies on the main sequence.

Which spectral class would the Sun likely move into upon becoming a red giant?

#Videos

What Causes a Red Giant's Surface to Cool? - YouTube

starsstellar evolutionastrophysicsred giantscooling