If a three hinged parabolic arch, (span $$l$$, rise h) is carrying a uniformly distributed load w/unit length over the entire span, A. Horizontal thrust is $$\frac{{{\text{w}}{l^2}}}{{8{\text{h}}}}$$ B. S.F. will be zero throughout C. B.M. will be zero throughout D. All the above

The correct answer is D. All the above.

A three-hinged parabolic arch is a type of arch that is supported by three hinges, one at each end and one at the crown. The arch is subjected to a uniformly distributed load, which means that the load is evenly distributed across the entire span of the arch.

The horizontal thrust is the force that the arch exerts on the supports. The shear force is the force that acts parallel to the cross section of the arch. The bending moment is the force that acts perpendicular to the cross section of the arch.

For a three-hinged parabolic arch, the horizontal thrust is given by the following equation:

$$H = \frac{{\text{w}}{l^2}}}{{8{\text{h}}}}$$

The shear force is given by the following equation:

$$V = 0$$

The bending moment is given by the following equation:

$$M = 0$$

Therefore, the horizontal thrust, shear force, and bending moment are all zero throughout the arch.