For a linearly variable infinite load, for a point P, the vertical stress σz is _________

• A. \(σ_z=\frac{q}{aπ} \left[xα+z\right] \)
• B. \(σ_z=\frac{q}{aπ} \)
• C. \(σ_z=\frac{q}{π}\left[\frac{az}{a^2+z^2}\right] \)
• D. \(σ_z=\left[xα-\frac{az}{(x-α)^2+z^2}(x-α)\right] \)