A. Galaxy. is the correct answer. a galaxy is a colossal grouping of solar systems, and stars that slowly orbit each other, and other galaxies.
B. nebula. is incorrect. a nebula is a large collection of dust and small meteoroids.
C. light year. is not correct. light year- a large unit of distance, often used when measuring the distance between galaxies.
D. solar system. is incorrect. solar system- a group of planets and a star.
