The correct answer is: B. Resultant force
A funicular polygon is a graphical representation of the internal forces acting on a beam. The ordinates of the funicular polygon represent the vertical components of the internal forces, which are the shear forces. The resultant force is the vector sum of all the internal forces acting on the beam.
Shear force is a force that acts parallel to the cross-section of a beam. It is caused by the bending moment, which is a force that acts perpendicular to the cross-section of a beam. The bending moment is caused by the load applied to the beam.
Equilibrium is a state of balance in which the forces acting on an object are equal in magnitude and opposite in direction. In the case of a beam, the equilibrium condition is that the resultant force and the bending moment are both zero.
Here is a diagram of a funicular polygon:
[Diagram of a funicular polygon]
The ordinates of the funicular polygon are the vertical distances from the line of action of the internal forces to the horizontal axis. The resultant force is the vector sum of all the internal forces, and it is represented by the diagonal line in the diagram.
I hope this explanation is helpful!