The correct choice is (c) εyz≠0

To explain: The Classical Plate Theory is based on the assumption that a straight line perpendicular to the plane of the plate is (1) inextensible, (2) remains straight, and (3) rotates such that it remains perpendicular to the tangent to the deformed surface, but In the SDT, we relax the normality assumption of CPT, i.e., transverse normal may rotate without remaining normal to the mid-plane. Thus, for a plate in the XY plane, the assumptions are equivalent to specifying εzz=0 only whereas εyz and εxz are non-zero.