Kevin and his mother are playing with an interesting squeaky toy. Kevin's mother squeezes the toy in front of him and then hides it under a blanket. Kevin has fun finding the toy under the blanket and then giving it back to his mother. After several rounds of this game, Kevin's mother hides the toy behind a pillow instead of under the blanket. Rather than looking behind the pillow, however, Kevin lifts the blanket to look for the toy. Which of the following statements is true?

a. Kevin is approximately 6 months old.
b. All of the statements are true.
c. Kevin is making the A-not-B error.
d. Kevin does not know the toy still exists.