Answer: The matter that has a indefinite volume, is a gas, as the air for example.
The matter that has definite volume and shape, is the solid matter, for example a piece of steel.
The matter that has a definite volume but no definite shape, is the liquid matter, which is the answer for this problem.
You can easily visualize this if you think in water; the liquid water is in liquid state, the vapor of water is in gas state, and the ice is in solid state.