a
(a) From figure, it is clear that \(\overrightarrow E \) at all points on the \(y\)-axis is along \(\hat i\). Here \(\overrightarrow E \) of all points on \(x\)-axis cannot have the same direction.
Here electric potential at origin is zero so no work is done in bringing a test charge from infinity to origin.
Here dipole moment is in -\(x\) direction (\(-q\) to \(+q\)).
Hence only option \((a)\) is correct.
