The Bystander Effect Is Most Likely to Occur

The bystander effect is most likely to occur

A) when someone is witnessing an emergency and there are several other people present.
B) when someone is witnessing an emergency and no one else is present.
C) in emergencies where people's actions are being videotaped.
D) in memory studies in which bystanders did not remember as much about an emergency as the individual who was the victim.