Which of the following complex species is not expected to exhibit optical isomerism?

Calculate the magnetic moment of the $Fe^{3+}$ ion in the $[Fe(CN)_6]^{3-}$ complex.

The pentaamminenitrocobalt $(III)$ ion exhibits which of the following properties?

The number of possible isomers for the square planar complex $K_2[PdClBr_2SCN]$ is .................

The type of isomerism shown by the complex $[CoCl_2(en)_2]$ is

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ The spin only magnetic moment value for $[Fe(CN)_6]^{3-}$ is $1.74 \ BM$,whereas for $[Fe(H_2O)_6]^{3+}$ is $5.92 \ BM$.
Reason $R:$ In both complexes,$Fe$ is present in $+3$ oxidation state.
In the light of the above statements,choose the correct answer from the options given below: