The total quantity of water with respect to the hydraulic gradient flowing through the capillary tube is given by _________

• A. ( q= frac{hi _w}{4 L} R^2 )
• B. ( q= frac{h _w}{4 L} R^4/i )
• C. ( q= frac{i _w}{8 } R^2 )
• D. ( q= frac{i _w}{8 } R^4 )