(i) [M(NCS)](-6+n): NCS is a medium filed ligand. Thus, splitting will be required medium amount of energy. Thus will be medium.
(ii) [MF6](-6+n): F is a weak field ligand. Thus, splitting will be low and low energy will be required. Thus, will be highest.
(iii) [M(NH3)]n+: NH3 is strong filed ligand. Thus, splitting will be high and high energy will be required. Thus, will be lower.
Thus, the correct sequence is:
A-(iii), B-(i), C-(ii)
Therefore, Option(4) is correct.
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