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