Which of the following correctly describes the hierarchy that exists in the universe? (3 points)

A galaxy refers to all existing matter, energy, and space that is held together by gravity.
A galaxy is a collection of planets, their moons, and other objects in orbit around a central star.
A solar system refers to all existing matter, energy, and space that is held together by gravity.
A solar system is a collection of planets, their moons, and other objects in orbit around a central star.

Which statement is true if the refractive index of medium a is greater than that of medium b? a. total internal reflection is possible when light travels from air to medium b to medium a. b. total internal reflection is possible when light travels from medium a to medium b. c. total internal reflection is possible when light travels from medium b to medium a. d. total internal reflection is possible when light travels from air to medium a. e. total internal reflection is possible when light travels from air to medium b.