Answer:A. deindividuation
Step-by-step explanation:
Deindividualization or deindividuation
Is a term used by psychologist to refer to how people tend to be less self aware when they are in the middle of a group that doesn't really know them and they would start to engage in doing things they wouldn't do if they were not in the middle of that crowd.
For example , a person who hates slapstick jokes may laugh at them because they're in the middle of the show where everyone laughs at someone doing that. This is mostly promoted by the fact that the person feels anonymous and they feel free to do things that they wouldn't do in their normal daily life.
Anonymity and Awareness is a drive of such behaviour, one may feel like they aren't responsible for their action if they are surrounded by a large number of people who are doing the same thing , they feel like it's a collective thing and they can not be singled out for such actions which are committed within a crowd.
This makes a person less self aware because they in a crowd they let their individuality die out and let the crowd rule their actions or behavior.
John is doing the same thing , he is taking his shirt off and dancing wildly because he is in the middle of 23, 000 cheering fans which makes him feel free to do this without any concern for individual responsibility.