ANS:D - all the above.

All the above. Terzaghi's analysis, which is widely used in geotechnical engineering, assumes the following:

1. Soil is homogeneous and isotropic: This assumption simplifies the analysis by considering the soil as having uniform properties in all directions.
2. Elastic zone has straight boundaries inclined at ψ = φ to the horizontal, and plastic zones are fully developed: This assumption describes the deformation behavior of the soil under loading. It considers that the elastic zone, where the soil behaves elastically, has straight boundaries inclined at an angle equal to the effective friction angle (ψ) to the horizontal, and the plastic zones, where soil failure occurs, are fully developed.
3. Failure zones do not extend above the horizontal plane through the base of the footing: This assumption implies that the failure surfaces develop beneath the footing and do not extend above the base. It simplifies the analysis by considering failure mechanisms that occur predominantly below the footing.