The correct choice is (b) The transverse deflection w and the normal derivative of w

The best I can explain: An examination of the boundary terms in the weak form of Classical Plate Theory suggests that the essential boundary conditions involve specifying the transverse deflection w and the normal derivative of w, which constitute the primary variables of the problem (like in the Euler-Bernoulli beam model). Hence, the finite element interpolation of w must be such that w and \(\frac{dw}{dn}\) are continuous across the inter-element boundaries in CPT elements.