The compatibility equation in terms of plane stress case is given by ________

• A. \((\frac{∂^2}{∂x^2} +\frac{∂^2}{∂z^2})=0\)
• B. \((\frac{∂^2}{∂y^2} +\frac{∂^2}{∂z^2})(σ_y+σ_z )=0\)
• C. \((\frac{∂^2}{∂x^2} +\frac{∂^2}{∂y^2})(σ_x+σ_y )=0\)
• D. \((\frac{∂^2}{∂x^2} +\frac{∂^2}{∂z^2})(σ_x+σ_z )=0\)