The partial differential equation\(5\left( {\frac{{{\partial ^2}{\rm{z}}}}{{\partial {{\rm{x}}^2}}}{\rm{\;}}} \right){\rm{\;}} + {\rm{\;}}6\left( {\frac{{{\partial ^2}{\rm{z}}}}{{\partial {{\rm{y}}^2}}}} \right){\rm{\;}} = {\rm{\;z}}\)

• A. elliptic
• B. parabolic
• C. hyperbolic
• D. none of these