Select the solid.

 - caramel sauce
 - coffee
 - air from a hair dryer
 - ring
Caramel sauce is a liquid. A liquid takes the shape of any container it is in. If you pour caramel sauce into a container, the caramel sauce will take the shape of that container. But the caramel sauce will still take up the same amount of space.
Coffee is a liquid. A liquid takes the shape of any container it is in. If you pour coffee into a different container, the coffee will take the shape of that container. But the coffee will still take up the same amount of space.
A ring is a solid. A solid has a size and shape of its own. A ring keeps its shape, even when you take it off your finger.
The air from a hair dryer is a gas. A gas expands to fill a space. A hair dryer uses a fan to blow warm air out. When the air leaves the hair dryer, the air expands to fill a much large space.