Which of the examples above illustrates a nonpolar solute in a polar solvent?

(Missing in the question):

-NH4Cl, ammonium chloride soluble in water, insoluble in Hexane.

-C10H8, naphthalene insoluble in water, soluble in Hexane.

-C2H5OH, ethanol soluble in water, soluble in Hexane.

-CO (NH2) 2, urea soluble in water, insoluble in Hexane.

While Hexane is anon polar solvent and water is a polar solvent,

So your answer is C10H8 naphthalene

C10H8 (as a non-polar) so it forms a layer in the water (which is a polar solvent) and at Hexane (which is a non-polar solvent) so C10H8 will dissolve in it.