Pavlov taught a dog to salivate at the sound of a ticking metronome by repeatedly pairing the ticking metronome with food. In this example, the ticking metronome is the before conditioning and the a after conditioning.

In this example, the ticking metronome is the neutral stimulus before conditioning and the conditioned stimulus after conditioning.

Explanation:

Food was the original unconditioned stimulus - the stimulus that causes an automatic, natural response. Salivating was the natural response to food. The metronome initially meant nothing to the dogs, meaning it was a neutral stimulus. However, Pavlov paired the sound of the metronome with the food. Because of that, the dogs associated the two and began to expect food every time they heard that sound. Now, the metronome is a conditioned stimulus, provoking the conditioned response of salivating in the dogs.

the first question's answer is a.