Which of the following statements are correct?
(i) In octahedral complexes, `d_z2, d_(x^2-y^2)` orbitals have higher energy than `d_(xy)`, `d_(yz)` and `d_(zx)` orbitals.
(ii) In tetrahedral complexes, `d_(xy), d_(yz), d_(zx)` orbitals have higher energy than `d_z2` and `d_(x^2-y^2)` orbitals.
(iii) The colours of complexes are due to electronic transitions from one set of d-orbitals to another set of orbitals.
(iv) `Delta_(tetrahedral)=9/4, Delta_(octahedral)`