Two long, parallel lines of charge are fixed at \(x = -d\) and \(x = +d\) in the \(xy\)-plane, carrying uniform linear charge densities \(+\lambda\) and \(-\lambda\), respectively. The electric potential is defined to be zero at the origin \((0, 0)\). Which of the following expressions gives the electric potential \(V(x)\) at a point along the \(x\)-axis in the region \(-d < x < d\)?