When he was 5 years old, Sunil was almost struck by lightning while walking through a forest during a rainstorm. Today, he is extremely afraid of trees. A behaviorist would say that he has acquired this fear by:

The answer is classical conditioning.

Explanation:

In classical conditioning, a conditioned stimuls is associated with an unrelated consequence. This produces what is known as conditioned response. In the example, the sight of trees is associated with lightning, which results in fear.

Russian scientist Ivan Pavlov demonstrated his classical conditoning theories when he rang a bell before feeding a dog. In time, the dog would start salivating at the sound of the bell.