‘Blue dwarfs’ and ‘Red giants’ respectively refer to:

(A) Moons of Jupiter
(B) Young star and Old star
(C) Old star and Young star
(D) None of these

The answer is: (C) Old star and Young star
A “blue dwarf” develops from a “red dwarf” after it has exhausted much of its hydrogen fuel supply. Therefore, blue dwarf is an old star while red giant is a young star.