The answer is D. This is because liquids take up the shape of the container they are in, so it is never definite. Where as solids stay the same shape.
Explanation
NaCl: Ionic crystal lattice forces
Hg: Metallic bonding
CO₂: London dispersion forces
CH₄: London dispersion forces
Li₂O: Ionic crystal lattice forces
Ag: Metallic bonds
Ionic crystal lattice forces are strong electrostatic force of attraction between oppositely charged ions arranged into a crystal lattice of ionic compound. NaCl and Li₂O are ionic compounds
London dispersion forces holds the molecules of carbon dioxide and methane. They are weak attractions found between non-polar (and polar) molecules.
Metallic bonds exists between Mercury and Gold atoms. This is due to sea of electrons present.
