Correct Answer - D
From V.B. theory, B.O. in CO i.e., `overset(-)C-=overset(+)O` : is 3, that of O=C=O is 2 while that of `CO_3^(2-)` lon is 1.33. Since the bond length increases as the bond order decreases i.e., CO lt `CO_2` lt `CO_3^(2-)`. Thus option (D) is correct.