Students are using balloons to describe the expanding universe model. The students blow up several balloons and put them on the floor. Each balloon represents a different galaxy. How should the students move or change the balloons to demonstrate how the universe is expanding?

a
All of the balloons should be moved to the center of the floor.
b
Each balloon should be deflated so that there is more distance between the surface of each balloon.
c
All of the balloons should be moved away from each other so there is more distance between them.