A. If pulling on an elastic rod causes it to contract perpendicular to the stretch direction (i.e. become thinner), is that proof of anisotropy? Or could the material be isotropic?
B. If a slab of material becomes thicker (taller) in proportion to its shear angle, is that necessarily anisotropic behavior, or could it be isotropic?
C. If twisting a cylindrical rod makes it shorter, no matter what the direction of twist, is this linear or nonlinear behavior?