Sublimation is the process of a substance transitioning directly from the solid to the gas state without passing through the liquid state. This process is endothermic, meaning it absorbs heat energy from its surroundings to provide enough energy for the molecules to overcome the intermolecular forces holding them in the solid state and escape into the vapour phase. Hence, the correct answer is option A - energy absorption

B. vapourization is the phase transition from a liquid to a gas (either through evaporation or boiling).

C. melting is the process where a solid changes into a liquid.

D. osmotic diffusion is a biological or chemical process related to the movement of solvents and solutes across a semipermeable membrane and is unrelated to the phase change of sublimation.