A parallel-plate capacitor consists of two large conducting plates of area \(A\) separated by a distance \(d\) in vacuum at positions \(x = 0\) and \(x = d\).

The capacitor is charged so that the plates carry fixed free charges \(+Q\) at \(x = 0\) and \(-Q\) at \(x = d\), after which it is isolated from the charging source.

An uncharged dielectric slab of thickness \(d/2\) and dielectric constant \(\kappa > 1\) is inserted between the plates, centered at \(x = d/2\) so that it occupies the region \(d/4 \le x \le 3d/4\).

Neglecting edge effects, which of the following graphs best represents the magnitude of the electric field \(E\) as a function of position \(x\) between the plates, from \(x = 0\) to \(x = d\)?