The compound that has the highest melting point amongst the following is:

Sodium chloride

Reason — Sodium chloride (NaCl) is an ionic compound. Ionic compounds have very strong electrostatic forces of attraction between oppositely charged ions, requiring a large amount of energy to break, so they have very high melting points.

Whereas, methane, ammonia and ethanol are covalent compounds with weak intermolecular forces, so they have low melting points.