Star is just a star its tiney compared to the Galaxy. There are many Galaxys inside the solar system so Galaxy has to be smaller than the solar system. The universe is everything and beyond so it has to be the largest.
Answer is D. A star is just a ball of light and gas. I could go more into it, but we don’t need to. A solar system is a bunch of plants and asteroids and other space objects orbiting a star. A Galaxy is a cluster of solar systems, like the Milky Way, or andromeda. And the universe is basically what we live in. An endless abyss, pretty much.
