A. Coulomb suggests that the relationship between shear strength and normal stress, is adequately represented by the straight line B. The generalised Mohr theory suggests that, though the shear stress depends on the normal stress, the relation is not linear C. Coulomb and Mohr suggest that a definite relationship exists among the principal stress and the angle of internal friction D. For an ideal pure friction material, the straight line passes through the origin. E. All the above.