Which Example Illustrates a Successive Negative Contrast Effect

Which example illustrates a successive negative contrast effect?

A) You are painting a room and run out of paint. You go to the paint store but forget the paint chip and accidentally purchase a lighter shade of the paint than wanted.
B) Meghan has always been paid $15 an hour for working in Dave's Diner and is happy. Travis, on the other hand, used to make $20 an hour at Mark's Place, but now makes $15 an hour at Dave's Diner. Travis feels cheated making the same amount as Meghan.
C) You are new to living on your own and to cooking. You prepare a meal with meat that is one day past the "sell by" date but experience no negative side effects. The next time you prepare a meal that is older than the "sell by" date, you become ill.
D) For ten years, employees at a company have pressed 9 to access an outside telephone line, but occasionally they have dialed 911 by mistake. After ten years the company changes its procedure, so that employees have to dial 7 for an outside line.