An uncharged, isolated spherical conducting shell has an inner radius \(a\) and an outer radius \(b\), centered at the origin \(x = 0\). A positive point charge \(+q\) is fixed inside the cavity on the \(x\)-axis at \(x = d\), where \(0 < d < a\). The electric potential is defined to be zero at infinity. Which of the following graphs best represents the electric potential \(V\) as a function of position \(x\) along the \(x\)-axis?