[Solution] $[Fe(CN)_6]^{3-}$: 1 unpaired e (1.73 BM); $[Fe(H_2O)_6]^{3+}$: 5 (5.92 BM); $[Fe(CN)_6]^{4-}$: 0 (0 BM); $[Fe(H_2O)_6]^{2+}$: 4 (4.90 BM). Answer (3).
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