CO
O₂⁻
CN⁻
NO⁺
O₂⁻ has one unpaired electron. Hence, it is paramagnetic. MOT configurations of O₂⁻: (σ1s)²(σ1s)²(σ2s)²(σ2s)²(σ2pz)²(π2px = π2py)(π2px = π2p1y) Hence, the correct option is B.