Equipotential surfaces are given as shown. The electric field intensity is ........

Show that the direction of the electric field at a given point is normal to the equipotential surface passing through that point.

Equipotential surfaces associated with an electric field which is increasing in magnitude along the $x$-direction are

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$: Work done by an electric field on moving a positive charge on an equipotential surface is always zero.
Reason $(R)$: Electric lines of force are always perpendicular to equipotential surfaces.
In the light of the above statements,choose the most appropriate answer from the options given below:

For an electric field that increases in magnitude along the $x$-direction,what is the nature of the equipotential surfaces?

Positive and negative point charges of equal magnitude are kept at $(0, 0, a/2)$ and $(0, 0, -a/2)$,respectively. The work done by the electric field when another positive point charge is moved from $(-a, 0, 0)$ to $(0, a, 0)$ is