Co-ordination number of Cr is 6. A complex entity with C₂O₄^–2, en, superoxide as ligands is [Cr(C₂O₄)_x (en)_y(O₂)_z]⁺ The ratio of numbers x and z is

Cobalt (Co) is a transition metal and as such it frequently forms complexes with ligands. Complexes of Co are generally paramagnetic and diamagnetic, which implies that the Co isotope present has six total electrons in its orbital shell (ii). 

There are a variety of ligand-ion complexes, whose coordination geometries can be explained using Crystal Field Theory (iii). 

The octahedral Co(II) ion has an effective nuclear charge of six, but forms complexes with bidentate ligands: in other words, it accepts two electron pairs from the ligand (iv). The d⁸ configuration is diamagnetic and for such a complex the O-O bond is ened (v).

Co-ordination of C1 = 6

C₂O₄^2-  and en bidentate ligands while O₂^- is unidentate.

SO, x= 1, y= 1, z= 2

Hence, Option A is correct.