The correct answer is the sphere. The amount of volume in the sphere is much larger than any other object when compared to the size of the surface area. The surface area of the sphere enables huge amounts of liquid for example to be held in spheres. It is much more efficient when it comes to that ratio than any other structure that is available such as a cone or a pyramid or a cube, or anything similar.
I think it refers to worldwide mutual dependence between nations/countries as we depend on each other for the key things like food etc. on a worldwide level.
