A) A large group of stars that orbit, or revolve, around each other
B) A small galaxy with millions to billions of stars that orbit, or revolve, around it
C) A star and all planets and moons that orbit, or revolve, around it
D) A star and all planets and other objects that orbit, or revolve, around it
Think of our solar system. Our solar system consists of 8 Planets. All of these revolve around a star(sun). Moons revolve around the planet, which revolves around the sun. Similarly, other Solar Systems work the same.