The Boussinesq settlement factor is given by _______

• A. \(F_B=\frac{3}{2} \frac{1}{1+(\frac{z}{a})^2}\)
• B. \(F_B=\frac{3}{2} \frac{1}{(1+(\frac{z}{a})^2)^\frac{5}{2}}\)
• C. \(F_B=\frac{3}{2} \frac{1}{(1+(\frac{z}{a})^2)^\frac{1}{2}}\)
• D. \(F_B=\frac{1}{(1+(\frac{z}{a})^2)^\frac{1}{2}}\)