Final answer:
Earth is a medium-size terrestrial planet formed from gas and dust, with an atmosphere comprised mainly of nitrogen and oxygen, distinct from the thick hydrogen and helium atmospheres of the giant planets. Its layered composition includes a solid and liquid iron core, establishing it as a rocky body capable of supporting liquid water and life.
Step-by-step explanation:
The statement that best describes Earth is that it was formed from gas and dust. Earth is a medium-size terrestrial planet with a diameter of approximately 12,760 kilometers and is composed primarily of heavy elements such as iron, silicon, and oxygen. Unlike the giant planets, which have thick atmospheres dominated by hydrogen and helium, Earth's atmosphere is thinner and comprised mainly of nitrogen and oxygen.
Earth features a solid iron core, a liquid iron outer core, a rocky mantle, and crust, making it very different from the gaseous outer planets or stars. Additionally, Earth's conditions are ideal to support liquid water and life, with an orbit that keeps its climate neither too hot nor too cold.