The state of stress in 3-dimension is given by the following determinant, the coefficient of σ2 is an invariant quantity which is equal to ________\(\begin{vmatrix}\sigma-\sigma x & -\tau yx & -\tau zx\\ -\tau xy & \sigma-\sigma y & -\tau zy\\ -\tau xz & -\tau yz & \sigma-\sigma z\end{vmatrix}\)

• A. σx+σy+σz
• B. σxσy+σyσz+σzσx-τxy2- τyz2- τzx2
• C. σxσyσz+2τxyτyzτzx-σxτxy2 -σyτyz2 -σzτzx2
• D. 1