Juan Is Leading His Team's Weekly Meeting

Juan is leading his team's weekly meeting. One of Juan's team members enters the meeting, and she appears visibly agitated and angry. Soon afterward, another team member enters who also appears to be upset and angry. Finally, the four other team members enter smiling and laughing. About 10 minutes into the meeting, Juan notices that all six team members are now smiling and speaking excitedly. Of the following, what is best possible explanation for why all of the team members are now smiling?

A) job satisfaction
B) employee engagement
C) job characteristics
D) emotional contagion