ANSWER
Liquid or gas
EXPLANATION
A solid is a material that has its molecules tightly packed together such that it is rigid and fixed in shape.
A gas is a material that has its molecules loosely bound together such that it has no shape.
A liquid is a material that has its molecules not as tightly packed as a solid but not as loosely bound as a gas.
The rigid and fixed shape of a solid makes it impossible for it to take the shape of any container, unlike liquids and gases that are able to do so.
Therefore, the answer is liquid or gas.
