The diagram depicts a simplified building model containing four identical heavy floors. The gap from the ground to the bottom floor is twice the separation between neighbouring floors. Between successive floors are equal numbers of vertical steel support rods whose mass is negligible compared with that of the floors. The rods have different diameters so that the stress in every rod is the same. What is the ratio $\dfrac{\text{diameter of bottom rods}}{\text{diameter of top rods}}$?
- A2
- B4
- C8
- D16