Which of the following is/are not compressible?
Solid
Compressibility is about reducing the free space between the particles.
Gas particles have a lot of free space than that of liquids and solids (due to less intermolecular force), thus they can easily compressed.
Liquids have more free space than solids, thus can be compressed easily than solids. Solids are least compressible or in some cases, impossible to compress (Due to very less intermolecular distance).