Final answer:
The compound with the highest melting point is ethane (C₂H₆).
Step-by-step explanation:
The compound with the highest melting point among the given options is D. C2H6, which is ethane. Ethane has a linear structure and stronger intermolecular forces compared to the other compounds. Methanol (A), CH3F (B), and CH4 (C) have weaker intermolecular forces and therefore lower melting points.