Correct option is C
Assumptions given by Rankine are:
1. The soil is homogeneous and isotropic, which means c, φ and γ have the same values everywhere, and they have the same values in all directions at every point.
2. The most critical shear surface is a plane.
3. The ground surface is a plane that may be horizontal or inclined.
4. The wall is infinitely long so that the problem may be analyzed in only two dimensions.
5. The wall moves sufficiently to develop the active or passive condition.
6. The wall surface at the back is vertical and smooth.
7. The retaining wall yields about the base and thus deformation condition satisfies plastic equilibrium.
