A Stranger Has Collapsed on a City Sidewalk Due to a Heart

A stranger has collapsed on a city sidewalk due to a heart attack. According to Darley and Latané, what is the first thing that must happen before a bystander helps in this emergency?

A) the bystander must be in a good mood
B) the bystander must have seen a helpful role model
C) the bystander experienced personal distress
D) the bystander must have pre-existing guilt
E) none of these