Identify the diamagnetic octahedral complex ions from below:
(A) \( [\mathrm{Mn(CN)_6}]^{3-} \)
(B) \( [\mathrm{Co(NH_3)_6}]^{3+} \)
(C) \( [\mathrm{Fe(CN)_6}]^{4-} \)
(D) \( [\mathrm{Co(H_2O)_3F_3}] \)
Choose the correct answer from the options given below: