Sublimation is the process through which the solid substance changes directly into vapours...so D is correct

The process for the change of a solid directly into its vapour is called sublimation. This is a physical change of state in which a solid substance is transformed into its gaseous state without passing through the liquid state.

Explanation:
Sublimation is a process in which a solid substance transforms directly into its gaseous state without going through the liquid state. This process occurs when the pressure is low, and the temperature is high. During sublimation, the solid absorbs heat energy and transforms into a gas, which is then cooled and condensed into a solid again.

Examples:
Some common examples of sublimation include the transformation of dry ice (solid carbon dioxide) into gas, the evaporation of mothballs, and the transformation of snow into water vapor without melting.

Applications:
Sublimation has several applications in various fields. In the field of chemistry, sublimation is used to purify substances. It is also used in the production of drugs, chemicals, and perfumes. In the field of medicine, sublimation is used to sterilize medical equipment. In addition, sublimation is used in the printing industry to transfer images onto various surfaces.

Conclusion:
Sublimation is a unique process that occurs when a solid substance transforms directly into its gaseous state without passing through the liquid state. This process has several applications in various fields and is used to purify substances, sterilize medical equipment, and transfer images in the printing industry.