Sublimation is a process in which a solid:
A.Changed into vapor
B.Changes into liquid form
C.Changes into another allotropic form
D.None of the above

Hint: We must know that sublimation is the process of converting a solid into vapor without going through a liquid phase. Sublimation is an endothermic process that occurs at temperatures and pressure below the triple point of substance.

Complete step by step answer:
We can call the specific change of state when a solid substance avoids the liquid state and moves directly into the gaseous state as sublimation. The process of sublimation occurs as the energy is being absorbed by the substance more rapidly from the surroundings, such that the process of melting never occurs.

Hence, option (A) is correct.
Sublimation occurs by absorption of heat that provides sufficient energy for few molecules to overcome the attractive forces of their neighbors and escape into the vapor phase.

Additional Information:
Sublimation is a physical change of state and does not describe the transformation of a solid to a gas in a chemical reaction.
Sublimation occurs by absorption of heat that provides sufficient energy for few molecules to overcome the attractive forces of their neighbors and escape into the vapor phase.
Few things that can sublime are water, iodine, arsenic, and solid carbon dioxide could sublimate normal temperatures and pressures. Few materials could be made to sublimate by creating conditions of low pressure.
In everyday life, sublimation is used in bathroom air fresheners. Naphthalene mothballs are used to scare moths and other domestic pets.
The process of sublimation happens freely with certain weather conditions such as low relative humidity and dry winds.
It also occurs at high altitudes, where the pressure of air is less than at lower altitudes.

Note:
We should not confuse between sublimation and desublimation/deposition. The process of the phase of solid to gas through the intermediate liquid state is called vaporization, whereas in sublimation, solid changes into vapor directly without going through a liquid state.