In case of octahedral compex, if the `e_(g)` orbitals `(d_(x^(2) - y^(2)) " and " d_(z^(2)))` are asymmetricaaly filled, their degeneracy is destroyed and the ligands approaching along `+Z` and `-Z` directions experiences different amount of repulsions than the ligands approaching along the `+X, -X, +Y " and " -Y` directions. As a result, the symmetrical nature of such complexes is lost and either elongation or compression along Z-axis taken place. Answer the following three questions based on the above situation.
In which of the following case, no such elongation or compressions are expected ?
A. `d^(4)` - weak ligands
B. `d^(5)`- weak ligands
C. `d^(7)`- strong ligands
D. `d^(9)`- strong or weak ligands
