What apparatus did Skinner use in his experiments?

The correct choice is the operant box, commonly known as the Skinner box. This apparatus was specifically designed to study operant conditioning by allowing researchers to observe the behavior of animals, primarily rats and pigeons, under controlled conditions. The box typically contains a lever or button that the animal can press to receive a reward, such as food or water, or to avoid a negative stimulus.

The use of the operant box enabled Skinner to meticulously analyze behavior in terms of reinforcement and punishment, thereby advancing the field of behavioral psychology. By manipulating the environment and observing the resulting behaviors, Skinner could draw conclusions about the principles of learning and behavior modification. This methodology laid the groundwork for various applications in behavior therapy and educational psychology.

The other options do not accurately represent the specific apparatus that Skinner utilized in his landmark studies on operant conditioning.