In the octahedral complex [Cr(OH ₂ ) ₆ ] ²⁺ which d-orbitals are higher in energy?

a. d _{z ²} and d _xy

b. d _{z ²} , d _{x ² -y ²} and d _{y ²}

c. d _xy , d _xz and d _{x ² -y ²}

d. d _{x ² -y ²} and d _{z ²}