Which of the following solids is held together by dispersion forces only?

Explanation

Iodine molecules are non polar, so the only attraction between them is the temporary induced dipole interaction known as the dispersion force, which is why iodine sublimes readily on gentle warming. Sodium chloride is ionic, diamond covalent network and copper metallic, all of which involve far stronger bonding. Dispersion forces still grow with molecular size, which is why iodine is a solid while chlorine is a gas.