When Two Black Disks Move Toward Each Other on a Computer

Multiple Choice

When two black disks move toward each other on a computer screen, overlap each other, and go to each other's starting position, people perceive that

A) the two disks pass through each other.
B) the two disks bounce off each other.
C) the two disks pass through each other when a brief sound occurs as they overlap.
D) the two disks bounce off each other when a brief sound occurs as they overlap.