O. H. Mowrer trained children to discontinue bed-wetting by arranging for an alarm to sound each time they wet their beds. This technique best illustrates a therapeutic application of:

classical conditioning.

Explanation:

Classical conditioning: In psychology, the term classical conditioning was proposed by one of the most influential psychologist and behaviorist named Ivan Pavlov. He has discovered the classical conditioning theory while experimenting on dogs and has included a few basic terms associated with it including unconditioned stimulus, unconditioned response, the conditioned stimulus, and conditioned response.

Classical conditioning is described as a learning theory that involves a conditioned stimulus that gives rise to a conditioned response after connecting with an unconditioned stimulus.

In the question above, the technique best illustrates the classical conditioning.