Which of the Following Research Topics on Problem Solving Would

Which of the following research topics on problem solving would have the lowest ecological validity?

A) How people plan their route through a hardware store, so that they can locate the items as quickly as possible.
B) How diners in a restaurant figure out how to divide a bill fairly among themselves.
C) How parents of preschoolers plan a birthday party.
D) How students in a geometry class use information from previous problems to solve the current problem.