Which one is not important in the learning process of Thorndike's Stimulus-Response Theory (S-R Theory)?

E.L. Thorndike's S-R Theory relies on Motive, Drive, Stimulus, and Trial-and-Error responses to form mechanical bonds.
Operant behaviour is a term coined by B.F. Skinner in his theory of Operant Conditioning. It refers to voluntary behavior that operates on the environment to produce consequences, distinct from Thorndike's classical trial-and-error framing.