Which of the following statements are correct?

A. Gagne has classified learning into Six (06) types in a hierarchical order.

B. The study of instrumental conditioning started from the puzzle box experiments on cats by Skinner.

C. The law of disuse states that other things being equal, when a modifiable connection between stimulus - response (S-R) is not made over a period of time, the strength of that connection is weakened.

D. Hull's theory of learning is called 'Drive-Reduction Theory'.

E. Shaping is the most important mechanism used in classical conditioning.

Choose the correct answer from the options given below: