What is sublimation?

Sublimation is defined as the direct transition of a substance from a solid phase to a gas phase without passing through the liquid phase. In the context of the options provided, choosing the process where ice transforms directly into water vapor accurately captures the essence of sublimation. This process is commonly observed in nature, such as when snow or ice gradually disappears in cold, dry conditions without melting first into liquid water.

Other processes mentioned in the choices involve phase changes that include an intermediate state—like melting ice into water or the evaporation of water—which do not fit the definition of sublimation. Thus, the focus on the direct change from ice to water vapor highlights the unique characteristic of sublimation as a distinct physical transition.