For a triangular and uniformly distributed semi-infinite loads, the shear stress τxz in the plane xz is ___________

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