Which of the Following Is an Example of Social Facilitation

Which of the following is an example of social facilitation?

A) Amy turns angry and violent after losing her terrier.
B) Natalia works better at meeting deadlines when she is not the only one working on a project.
C) Joe and a group of tourists he is guiding witness a crime but do not move forward to help, thinking that the other witnesses will.
D) Tom allows himself to get persuaded by his peers to drink a few extra beers.