Step 1 - Defining the states of matter in terms of its properties
The three main states of matter can be defined according to their properties, such as shape, volume and compressibility.
The solid state has a definite shape. Note a ice cube will not change its form no matter in which pot you put it. It also has a definite volume and a very low compressibility.
Liquids, on the other hand, can change their form: they will occupie the whole form of the vessel you put them. But the volume will not change. They also have a definite volume and a low compressibility.
Gases, in turn, do not have a definite volume: they will occupie the whole volume available, be it a small bottle or a room. They also have indefinite shapes and are very compressible.
Step 2 - Chossing the right alternative
As we have seen, indefinite shape, definite volume and low compressibility are properties of liquid matter.
The correct alternative thus is item b) liquid.