After receiving a reward for escaping the puzzle box, the cats a. appeared to enjoy the box more b. escaped more slowly c. gradually learned to escape more quickly d. increased the length of time in the box

Option (C) is the correct answer.

Explanation:

Once the cats escaped from the puzzle box, then in their conscious mind they tend to develop the image of path through which they had escaped.

So, form next time onward they tend to move more quickly because they already know the path through which they had to escape.

Hence, we can conclude that after receiving a reward for escaping the puzzle box, the cats gradually learned to escape more quickly.