In an experiment, participants are paired up, and each member of the pair goes into a separate closed room. One of the pair is instructed to maintain a neutral expression, while the other is instructed to smile for the duration of the experiment. After 10 minutes, both participants record their current mood. If this experiment is repeated for many trials, which is the most likely result? A : The neutral group will have a more positive mood.

B : The moods of participants will be entirely random.

C : The two groups will report the same mood.

D : The smiling group will have a more positive mood.