Question

13. A basic observation of a star is how bright it appears. This brightness is known as the star's A. absent magnitude. B. apparent magnitude. C. absolute magnitude. D. luminosity.

Answer 1

Star brightness is defined by either D. apparent magnitude - when we measure it from Earth (that is how bright it is from Earth) - this is the closest to "basic observation" and the best answer
or by absolute magnitute - how bright it would be at a certain distance (this allows to compare the brightness).