The molecular solid with the highest melting point would be the one with the strongest intermolecular forces. Among the given options, carbon dioxide (CO2) has the strongest intermolecular forces due to its linear molecular geometry, which allows for efficient dipole-dipole interactions. The other options, such as methane (CH4) and neopentane (C5H12), have weaker intermolecular forces due to their non-polar or bulky molecular structures. Therefore, carbon dioxide (CO2) would have the highest melting point among the given molecular solids.