According to crystal field theory d-orbitals split up in octahedral field into two sets.`d_("xy")d_("yx")d_("zx")` have lower energy and `d_(x^(2)-y^(2))" "and" "d_(z^(2))` have higher energy. The difference in energy of these two sets of d-orbitals is called crystal field splitting energy denoted by `Delta_(0)`. In tetrahedral field `d_(x^(2)-y^(2))" "and" "d_(z^(2)` have lower energy whereas `d_("xy")d_("yz")d_("zx")` have higher energy. The difference in energy is denoted `Delta_(t)`. `Delta_(0)` can be determined by measuring `lambda_("max")` for absorption and converting into energy units. `Delta_(0)` depends upon nature of metal ions as well as nature of ligands. The magnitude of `Delta_(0)` also decides low energy levels are filled. which one of the following has the highest magnetic momentA. `[CoF_(6)]^(3-)`B. `[Ni(H_(2)O)_(6)]^(2+)`C. `[Fe(CN)_(6)]^(3-)`D. `[Cu(NH_(3))_(4)]^(2+)`