The coefficient of curvature from the grain size distribution curve is given by:

• A. \(\frac{{{D_{60}}}}{{{D_{10}}}}\)
• B. \(\frac{{D_{30}^2}}{{{D_{10}}{D_{60}}}}\)
• C. \(\frac{{D_{60}^2}}{{{D_{10}}{D_{30}}}}\)
• D. \(\frac{{{D_{30}}}}{{{D_{10}}}}\)