Answer
Set C is correct!
Work Step by Step
Recall the equation describing the relationship between Electric field strength and potential:
E = $-\frac{\Delta{V}}{\Delta{s}}$
Since E is a vector, the negative in the equation indicates that it points in the direction of decreasing electric potential: a, b and c satisfy this condition.
The equation also indicates that E and $\Delta{s}$ are inversely proportional, that is electric field strength increases as the distance between equipotential lines decreases. So, set C should be the correct answer.
