A thin circular wire loop of radius \(R\) lies in the \(xy\)-plane and carries a steady current \(I\). The magnitude of the magnetic field along the central \(z\)-axis perpendicular to the loop is given by \(B(z) = \dfrac{\mu_0 I R^2}{2(R^2 + z^2)^{3/2}}\), where \(z\) is the distance from the center of the loop. Which of the following expressions represents the approximate magnitude of the magnetic field at a point on the axis very far from the loop (\(z \gg R\))?