In pavlov’s research, dogs learned that the sound of a metronome predicted the arrival of food, so the dogs salivated at the sound of the metronome. in this research, classical conditioning occurred in part because the elicited a(n)

 In this research, classical conditioning occurred in part because the Stimulus  elicited a response.

Explanation:

After conditioning, Pavlov was able to:

Form a conditioned response , that was a learned response to the previously neutral stimulus.  For the case of the dogs, the conditioned response would be the salivation, as they heard the sound of whistling.

Unconditioned stimulus existed before and naturally triggers a response, like the sole presence of food to a dog, if the dogs smells the food this will occur unconditioned. It means also it is unlearned, in an unconditionated way.

The key for understanding Pavlov's achievements was to observe how he was able to create the conditioning conditions, See below :)

pretty sure a is right