Which one of the following does not exhibit geometrical isomerism?

Which of the following is a chiral complex? Here $en = \text{ethylenediamine}$.

The theoretical value of the magnetic moment for the complex ion $[Co(NH_3)_6]^{2+}$ is ...... $B.M.$

Which of the following ions has a magnetic moment of $5.93 \ BM$?

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:

Among the following complexes $(K-P)$,
$K_3[Fe(CN)_6]$ $(K)$,$[Co(NH_3)_6]Cl_3$ $(L)$,$Na_3[Co(ox)_3]$ $(M)$,$[Ni(H_2O)_6]Cl_2$ $(N)$,$K_2[Pt(CN)_4]$ $(O)$ and $[Zn(H_2O)_6](NO_3)_2$ $(P)$,the diamagnetic complexes are