Final answer:
Imitation is a learned behavior in animals.
Step-by-step explanation:
Thorndike's research on spontaneous imitation with cats and dogs in puzzle boxes led him to conclude that imitation is a learned behavior in animals (option B).
Through his experiments, Thorndike observed that animals can learn to imitate certain behaviors by observing and copying the actions of other animals.
Therefore, the correct answer to the question is B) Imitation is a learned behavior in animals.