What type of retaining wall uses the weight of the soil on its footing to achieve soil stability?

The correct choice is gravity. Gravity retaining walls primarily rely on their own weight to resist the lateral pressure exerted by the soil they are holding back. These walls are usually made from heavy materials like concrete or stone, which provides the necessary mass to counteract the forces of the soil. As the weight of the wall itself is combined with the pressure of the soil behind it, this design effectively maintains stability and prevents the wall from toppling over.

In contrast, cantilever walls, while they do utilize a vertical component to resist lateral pressures, also rely on a footing and the leverage provided by their vertical portion to generate stability, rather than just the weight of the soil. Counterfort walls include additional structural support (the counterforts) to enhance stability, further differentiating them from gravity walls. Therefore, gravity walls exemplify the principle of using their own weight to achieve soil stability effectively.