What type of matter has both a changeable shape and volume?

Gas is the correct answer because gases have neither a fixed shape nor a fixed volume. Instead, they expand to fill the shape and volume of their container. This is due to the high energy of gas particles, which allows them to move freely and widely, spreading out to occupy the available space.

In contrast, liquids have a definite volume but take the shape of their container, which means they do not change volume. Solids have both a fixed shape and a fixed volume, as their particles are tightly packed together in a structured arrangement. Sublimated matter refers to a phase change from solid to gas without becoming liquid, but it does not inherently define a state of matter that maintains both changeable shape and volume. Thus, gas is the only state of matter that possesses both characteristics of changeable shape and volume.