The process described in the question is called sublimation. Sublimation occurs when a solid substance changes directly into a gas without going through the intermediate stage of becoming a liquid. This is different from other processes such as evaporation and condensation.

Option 1: Condensation. Condensation is the process by which a gas or vapor changes into a liquid. It involves the cooling of the gas or vapor to reduce its energy and allow the particles to come closer together and form a liquid.

Option 2: Evaporation. Evaporation is the process by which a liquid changes into a gas. It occurs when the molecules of the liquid gain enough energy to overcome the forces of attraction between them and escape into the air as gas.

Option 3: Sublimation. This is the correct answer. Sublimation is the process in which a solid directly changes into a gas without passing through the liquid state. It usually occurs when the temperature and pressure conditions are such that the solid`s molecules have enough energy to break free from their fixed positions and become gas particles.

Option 4: Diffusion. Diffusion is the movement of particles from an area of high concentration to an area of low concentration. It is not specifically related to the process of a solid turning into a gas