Consider a two-dimensional flow through isotropic soil along x direction and z direction. If h is the hydraulic head, the Laplace’s equation of continuity is expressed as

• A. \(\frac{{\delta h}}{{\delta x}} + \frac{{\delta h}}{{\delta z}} = 0\)
• B. \(\frac{{{\delta ^2}h}}{{\delta {x^2}}} + \frac{{{\delta ^2}h}}{{\delta x\delta z}} + \frac{{{\delta ^2}h}}{{\delta {z^2}}} = 0\)
• C. \(\frac{{{\delta ^2}h}}{{\delta {x^2}}} + \frac{{{\delta ^2}h}}{{\delta {z^2}}} = 0\)
• D. \(\frac{{\delta h}}{{\delta x}} + \frac{{\delta h}}{{\delta x}}\frac{{\delta h}}{{\delta x}}\frac{{\delta h}}{{\delta z}} + \frac{{\delta h}}{{\delta z}} = 0\)