From the information given in the passage, what is the most likely configuration of the cobalt d-electrons for the species (A) CoCl63− and (B) CoNO263−?

Cl⊖ always behaves as weak field ligand so high spin complex formed. Also here ∆o is not sufficient to overcome pairing energy P, NO2Θ with Co behaves as strong field ligand and hence low spin complex. Also  ∆o > P and hence pairing takes place.