Final answer:
Octane, being a nonpolar molecule, would be a good solvent for C10H8 (naphthalene) which is also nonpolar. I2 might also dissolve to some extent. However, NaCl and H2O, being ionic and polar, respectively, would not dissolve well in octane.
Step-by-step explanation:
Looking at the molecular structure of octane (CH3(CH2)6CH3), we can determine that it is a nonpolar molecule. This is due to the even distribution of electrons across the molecule and the lack of significant electronegative atoms that would create a dipole moment. The principle of like dissolves like in chemistry suggests that nonpolar solvents are good at dissolving nonpolar solutes, while polar solvents are good at dissolving polar and ionic solutes.
Given the choices of I2 (iodine), NaCl (sodium chloride), H2O (water), and C10H8 (naphthalene), the substance that would be best dissolved by octane is naphthalene (C10H8). This is because naphthalene is a nonpolar organic compound similar in nature to octane, which makes it solvable in a nonpolar solvent. I2 could also be considered soluble to some extent because it is nonpolar, but NaCl and H2O, which are ionic and polar respectively, would not dissolve well in octane due to their distinct polar characteristics compared to octane's nonpolarity.