The unit load method used in Structural analysis is

For a linear elastic structural system, minimization of potential energy yields

The plane frame below is analyzed by neglecting axial deformations. Following statements are made with respect to the analysis :

$$1.$$$$\,\,\,\,\,\,\,$$ Column $$AB$$ carries axial force only.
$$2.$$$$\,\,\,\,\,\,\,$$ Vertical deflection at the center of beam $$BC$$ is $$1mm.$$

Which of the following applies?

For the plane truss shown in the figure, the number of zero force members for the given loading is