Operant or Classical Conditioning Reflect Early Approaches Towards Changing Behaviour

Operant or Classical Conditioning reflect early approaches towards changing behaviour.
Which description correctly describes research into Operant Conditioning?

A) Thorndike (1874-1949) , who observed the behaviour of cats trying to escape from homemade puzzle boxes.
B) Pavlov's (1960) experiment with dogs
C) Skinner's (1953) approach to conditioning based on reinforcement, punishment, and extinction
D) Pollitt's article (2010) example of how training and development can develop leadership skills.