Which stars have low temperatures and high luminosities

A. Red giants

B. White dwarfs

C. Main sequence stars

Red giants have low temp but high luminosity while white dwarfs have a very high temp but low luminosity main sequence stars are just mixed

Red giant.

Explanation:

Red giant star is the last stage of stellar evolution. Red giant star has the size of around 100 million to 1 billion kilometers in diameter.

Red giant star has low temperature, ranges only from 2200 to 3200°C. The red star shows high luminosity more than 3000 times as compared with sun.

Thus, the correct answer is option (A).