Pavlov believed that classical conditioning occurs if and only if the CS and the US are

A) physically similar.
B) both followed by positive reinforcement.
C) equally intense (for example, equally loud) .
D) presented at nearly the same time.

Classical Conditioning

A conditioning technique where two stimuli are repeatedly connected; the reaction, at first prompted by the second stimulus, ultimately becomes prompted by only the first stimulus.

Unconditioned Stimulus (US)

A stimulus that naturally triggers a response without the need for prior learning.

Conditioned Stimulus (CS)

In classical conditioning, a previously neutral stimulus that, after being repeatedly paired with an unconditioned stimulus, evokes a conditioned response.