In Pavlov's work on classical conditioning with dogs the bell became and because it was originally neutral but it became paired with the UC (food)

The anwer is conditioned stimulus.

Explanation:

In classical conditioning, any neutral stimulus can become conditioned when associated with an unrelated consequence (called unconditioned stimulus).

Pavlov's experiment used the sound of a bell to cause a conditioned response, this is, the salivation of the dog. However, his theories demonstrate that the sound of a bell could have been replaced for any other stimulus, such as a whistling or clapping sound. These would have become conditioned if constantly followed by the food.

The first one.

Explanation:

There was a feeling of loss as many citizens lost their homes and loved ones as a result of the violence of war.