Question

what is luminosity?
o the amount of energy a star emits in a unit of time
o the brightness of a star as seen from earth
o the average temperature of a star during its life cycle
o the degree of shift toward the red end of the spectrum

Explanation:

Luminosity is defined as the total amount of energy a star emits per unit time. It is an intrinsic property of the star, independent of its distance from Earth. The brightness of a star as seen from Earth is called apparent - magnitude. The average temperature of a star is related to its color and spectral type, not luminosity. The degree of shift toward the red - end of the spectrum is related to redshift.

Answer:

the amount of energy a star emits in a unit of time