Keegan Notices That His Favourite 99-Cent Candy Bar Seems Lighter

Keegan notices that his favourite 99-cent candy bar seems lighter than usual and so he checks the label and finds that it is lighter by 15 grams. He decides to buy a larger candy bar instead and doesn't notice that the $1.49 candy bar also is lighter by 15 grams. Keegan's behaviour 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) the larger a weight is, the greater the change must be before one can detect a difference.
D) jnd's are unpredictable, because sometimes he can and sometimes he can't detect a 15-gram change.