While Waiting in Line to Buy One Cheeseburger for $1

Multiple Choice

While waiting in line to buy one cheeseburger for $1.50 and a medium drink for $1.00, Sally notices that she could get a value meal that contains both the cheeseburger and medium drink and also a medium order of fries for $2.75. She thinks to herself, "Is it worth the extra 25 cents to get the medium fries?" To an economist, Sally's decision is an example of

A) marginal decision making.
B) basing decisions on total, rather than marginal, value.
C) an unintended consequence.
D) the fallacy of composition.