Answer
a. Melting.
b. Sublimation.
c. Freezing.
d. Deposition.
Work Step by Step
Melting - when a solid substance changes to liquid.
Freezing- when a liquid substance changes to solid.
Sublimation- when a solid substance changes to a gas, without passing through the liquid state.
Deposition- the opposite of sublimation, when a gas changes to a solid substance.