In the psychology of learning, regarding the relationship between Stimulus (S) and Response (R) among Thorndike's Trial and Error Theory, Pavlov's Classical Conditioning Theory, and Skinner's Operant Conditioning Theory, which of the following analytical statements is most appropriate?

Thorndike's trial and error theory is mainly based on S-R (Stimulus-Response), where the Law of Effect is important. In Ivan Pavlov's classical conditioning, a relationship between a stimulus (like a bell) and a response is also established. In contrast, B.F. Skinner's operant conditioning is based on R-S (Response-Stimulus), where the organism responds first and the subsequent reinforcement determines its frequency.