gas
SHAPE
A gas can change shape but it doesn't change volume, a liquid also changes shape but doesn't change volume.
the answer is liquid... as my science teacher says.
A fluid has a definite volume, but it does NOT have a definite shape: its shape changes depending on the container it is in.
The state of matter that keeps the same volume but changes shape when it changes container is a liquid. Liquids do not have a fixed shape but take the shape of their container due to their ability to flow and fill the container.
Shape, mass or volume.
liquid
Stress
a liquid
A gas.
Gases do that.
pressure