Emily Does a Study to See If People Who Are

Emily does a study to see if people who are learning difficult tasks are hungrier than people who are learning easy tasks. She carefully develops one task that is easy and one that is difficult, controls the temperature and noise of the room for each group, and randomly assigns people to either the difficult or the easy group. She provides each group with ice cream and observes how many people eat it in each group. There is a confounding variable in her experiment. What is it?

A) she shouldn't have controlled for noise and temperature
B) some people might be offended that they got the easy group rather than the difficult group or vice versa
C) she did not use deception
D) she did not treat her subjects equally in all respects except for the variable that is of particular interest
E) some people might not like or be able to eat ice cream