A uniform bar lying in the x – direction is subjected to pure bending. Which one of the following
tensors represents the strain variation when bending moment is about the z – axis
(p, q and r contents)?
(a) $\bigl(\begin{smallmatrix} py&0 &0 \\0 &qy & 0\\ 0&0 &ry \end{smallmatrix}\bigr)$
(b) $\bigl(\begin{smallmatrix} py& 0 & 0 \\ 0 & qy & 0\\ 0& 0 & 0 \end{smallmatrix}\bigr)$
(c) $\bigl(\begin{smallmatrix} py& 0 & 0 \\ 0 & py & 0\\ 0& 0 & py \end{smallmatrix}\bigr)$
(d) $\bigl(\begin{smallmatrix} py& 0 & 0 \\ 0 & qy & 0\\ 0& 0 & qy \end{smallmatrix}\bigr)$