To determine the order of orbitals by decreasing energy, we need to use the (n+l) rule, where "n" is the principal quantum number and "l" is the azimuthal quantum number for the orbital type (s, p, d, f correspond to l values of 0, 1, 2, 3, respectively). The rule states that the sum of n + l determines the energy order. If two orbitals have the same n + l value, the orbital with the lower n value has lower energy.
Thus, the order of orbitals from highest to lowest energy is: 5f > 6p > 5p > 4d.
The correct option is: 5f > 6p > 5p > 4d.