Implosion is the process of strategically placing explosives at various key points along a building's main supports. Before the blasters load, or wire, the building with explosives, they remove as many interior walls as possible. Which of the following best explains why they might do this?

to eliminate the need for undermining
to allow the building to collapse inward upon itself
to reduce the amount of non-structural demolition needed
to provide more room to place explosives