The correct option is
The particles in solids are tightly packed and this causes rigidity in their shape.
Liquids are fluids, i.e. - they can flow, but their volume cannot be altered by the application of pressure. Thus, liquids are incompressible.
Gases are also fluids, but they have no fixed volume. They spread out to occupy the volume of the entire container. Due to large interparticle space, gases are compressible.