Step 1: Approach
Use the force direction.
Step 2: Geometry
The electric field is perpendicular to an equipotential surface. A displacement along the surface is perpendicular to the field, so $\vec F\cdot d\vec s=qE\,ds\cos90^\circ=0$.
Step 3: Answer
No work is done, option (D).
Final Answer:
The potential difference is zero on an equipotential surface, so no work is done, option (D).
\[ \boxed{\text{No work is done}} \]