Here's why:

* Rock: Asteroids are rocky bodies that orbit the sun. They are much smaller than planets.

* Liquid: While some celestial objects like comets have a small amount of liquid water, they are primarily made of ice and dust. There are no large, liquid bodies orbiting the sun.

* Gas: Gas giants like Jupiter, Saturn, Uranus, and Neptune are made mostly of gas. They are planets and not simply orbiting gas.

Let me know if you have any other questions!