Behavioral infection: refers to the process in which a group of people moves from one person to another, until a group of people acts together. Which of the following concerns behavioral infections? ['A person occasionally looks up at the sky. The people behind him think that there is something abnormal in the sky, and they all look up to the sky.', 'Li Dong at the meeting called on everyone to treat the factory as a home, work together to overcome difficulties, and everyone applauded in agreement.', 'College students are more pragmatic in applying for jobs, and have gone to the labor market to find opportunities.', 'Lao Li and Lao Wang talked together and found that everyone was surprised by the endless stream of draft shows.']