Which of the Following Statements About Distraction and Social Facilitation

Which of the following statements about distraction and social facilitation is true?

A) Individuals who are in the same room, but unable to view the performance of another person, can still serve as a distraction.
B) In order to be a distraction, individuals must perform tasks in front of observers.
C) Distraction impairs performance on difficult tasks that require individuals to focus their attention.
D) People's performance on simple tasks suffers when performed in a crowd of people.