Equipotential surfaces are shown in fig, then the electric field strength will be:

A. 100 V/m along X-axis
B. 100 V/m along Y-axis
C. 200 V/m at an angle 120° with X-axis
D. 50 V/m at an angle 180° with X-axis

To determine the electric field strength based on the equipotential surfaces, we need to understand the relationship between electric field lines and equipotential surfaces.

In electrostatics, electric field lines are always perpendicular to equipotential surfaces. This means that the electric field lines point from higher potential to lower potential and are always perpendicular to the equipotential surfaces.

Let's analyze the options given:

A. 100 V/m along the X-axis: This is not correct because if the equipotential surfaces are shown in the figure, the electric field lines should be perpendicular to those surfaces, not along the X-axis.

B. 100 V/m along the Y-axis: This is also not correct for the same reason as option A.

C. 200 V/m at an angle of 120 degrees with the X-axis: This is a possibility. If the electric field lines are at an angle of 120 degrees with the X-axis, they could be perpendicular to the equipotential surfaces, as long as those surfaces are not parallel to the X or Y-axis.

D. 50 V/m at an angle of 180 degrees with the X-axis: This is not correct because an angle of 180 degrees with the X-axis means that the electric field lines would be in the opposite direction of the X-axis, which is not consistent with the perpendicularity between electric field lines and equipotential surfaces.

So, option C (200 V/m at an angle of 120 degrees with the X-axis) is a reasonable choice based on the information provided about the equipotential surfaces and their relationship with electric field lines.