Classical conditioning or Pavlovian conditioning is a type of learning where the conditioned stimulus (CS) appears to indicate the existence of the second stimulus, i.e., the unconditioned stimulus (US), which is a stimulus that causes a response in the organism. Conditioned response is a learned response to the early neutral stimulus. US is generally a biologically relevant stimulus like pain or food, which evokes a response from the start and is is termed as unconditioned response (UR).

Which of the following options give(s) the correct name for classical conditioning?