$[Co(NH_3)_4Cl_2]^+$ exhibits

Which cyano complex exhibits the minimum magnetic moment?

The magnetic moment of $X^{n+}$ is $\sqrt{24} \ B.M.$ Find the number of unpaired electrons and the value of '$n$' respectively. (Atomic number of $X = 26$)

Which of the following compounds may show optical activity?

The compound$(s)$ that exhibit$(s)$ geometrical isomerism is(are):
$A$. $[Pt(en)Cl_2]$
$B$. $[Pt(en)_2]Cl_2$
$C$. $[Pt(en)_2Cl_2]Cl_2$
$D$. $[Pt(NH_3)_2Cl_2]$

Among the species given below,the total number of diamagnetic species is. . . . . $H$ atom,$NO_2$ monomer,$O_2^{-}$ (superoxide),dimeric sulphur in vapour phase,$Mn_3O_4$,$(NH_4)_2[FeCl_4]$,$(NH_4)_2[NiCl_4]$,$K_2MnO_4$,$K_2CrO_4$