solution:

Choice (I) is the appropriate response.

Enthalpy of sublimation of a substance is equivalent to enthalpy of combination + enthalpy of vapourisation.

Sublimation is immediate change of strong to fume, i.e., strong → fume

Writing in two stages, we have strong → fluid → fume.

Strong → fluid requires enthalpy of combination.

Fluid →vapour requires enthalpy of vapourisation