Keegan Notices That His Favorite 55-Cent Candy Bar Seems Lighter

Keegan notices that his favorite 55-cent candy bar seems lighter than usual, and so he checks the label and finds that it is lighter by ½ ounce. He decides to buy a larger candy bar instead and doesn't notice that the 99-cent candy bar also is lighter than it used to be by ½ ounce. Keegan's behavior illustrates the fact that:

A) the just noticeable difference is not a reliable measure of psychophysiological judgment.
B) sensory adaptation may occur in the short time between holding one candy bar and then the other.
C) jnds are unpredictable because sometimes he can and sometimes he can't detect a ½ ounce change.
D) the larger a weight is, the greater the change must be before one can detect a difference.