In one of Thorndike's puzzle boxes, a door would fall open when a cat stepped on a treadle, thus allowing the cat to reach food outside the box. Eventually the cat would step on the treadle as soon as it was put into the box. Thorndike concluded that .
a. the reasoning ability of cats is quite remarkable
b. treadle stepping increased because it had a "satisfying effect"
c. the treadle is a CS for stepping
d. learning meant connecting the treadle with freedom and food