The correct answer is: C. Both force polygon and funicular polygon close.
A force polygon is a diagram that shows the directions and magnitudes of all the forces acting on an object. The funicular polygon is a diagram that shows the lines of action of all the forces acting on an object. If both the force polygon and the funicular polygon close, then the system of forces is in equilibrium.
A system of forces is in equilibrium when the net force acting on the object is zero. This means that the object will not move. The force polygon and the funicular polygon can be used to determine if a system of forces is in equilibrium.
The force polygon is constructed by drawing a line for each force, with the length of the line proportional to the magnitude of the force. The lines are drawn starting from a common point, and the arrows on the lines show the direction of the forces. If the force polygon closes, then the system of forces is in equilibrium.
The funicular polygon is constructed by drawing a line for each force, with the direction of the line being the same as the direction of the force. The lines are drawn starting from a common point, and the length of the line is proportional to the component of the force that is perpendicular to the line. If the funicular polygon closes, then the system of forces is in equilibrium.
In conclusion, the correct answer is: C. Both force polygon and funicular polygon close.