When energy changes from one form to another, it is called energy A. radiations
B. transmissions
C. solutions
D. transformations

(see below)

Explanation:

Using the process of elimination:

It's not energy radiations because radiation is a way energy is transferred.

It's not energy transmissions because that's the transfer of energy from one medium to another, like the sun to a black construction paper through radiation. There are three ways of transmission: radiation, convection, and conduction.

It's not solutions because a solution is a homogenous mixture where it is uniform in composition and appearance throughout. Also, the term "energy solutions" makes no sense whatsoever.

It's most likely energy transformations because energy transformation, also called energy conversion, is the process of changing energy from one form to another.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .