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Solution-

Shapes of different d-orbitals are 

Also,

According to Crystal Field Theory, as a ligand approaches the metal ion, the electrons in the d-orbitals and those in the ligand repel each other due to repulsion between like charges. Thus the d-electrons closer to the ligands will have a higher energy than those further away which results in the d-orbitals splitting in energy. 

The most common type of complex is octahedral; here six ligands form an octahedron around the metal ion. In octahedral symmetry the d-orbitals split into two sets with an energy difference

The splitting of the d orbitals in an octahedral field takes place in such a way that , experience a rise in energy and form the e_g level, while d_xy, d_yz and d_zx experience a fall in energy and form the t_2g level.