Which One of the Following Examples Best Reflects the Cocktail

Which one of the following examples best reflects the cocktail party phenomenon?

A) Students become overwhelmed when too much is going on in the classroom at once.
B) Students working in a small group can hear what one student is saying even though students in other groups are also talking.
C) When a dog walks into the classroom, the students' attention is temporarily distracted from their independent seatwork assignment.
D) Students pay more attention when they are enjoying themselves.