Which Is an Example of Social Contagion

Which is an example of social contagion

A) New recruits are expected to do many pushups, and punished if they don't. The harsher the punishment, the more succeed.
B) Five kids sit sideways on a school bus. Soon most of the kids are doing the same.
C) One person facing the wrong direction in an elevator causes other passengers to become anxious.
D) The darker the alleyway, the more people avoid it.