Which Statement Demonstrates the Free-Operant Paradigm

Multiple Choice

Which statement demonstrates the free-operant paradigm?

A) After reaching the end of a maze, a rat is returned to the starting point by the experimenter.
B) When a cat escapes from a puzzle box, the experimenter puts the cat back in.
C) A rat in a Skinner box can press a bar at any time to receive food.
D) After reaching the end of a maze, a rat is put back inside its home cage.