The one that will show optical activity is: $(en = \text{ethane-}1,2\text{-diamine})$

In which of the following compounds does the central metal atom have the maximum number of unpaired $e^-$?

Match List-$I$ with List-$II$ :

List-$I$	List-$II$
$(a).$ $[Co(NH_3)_6][Cr(CN)_6]$	$(i).$ Linkage isomerism
$(b).$ $[Co(NH_3)_3(NO_2)_3]$	$(ii).$ Solvate isomerism
$(c).$ $[Cr(H_2O)_6]Cl_3$	$(iii).$ Coordination isomerism
$(d).$ $cis-[CrCl_2(ox)_2]^{3-}$	$(iv).$ Optical isomerism

Choose the correct answer from the options given below:

An octahedral complex having molecular composition $Co \cdot 5NH_3 \cdot Cl \cdot SO_4$ has two isomers $A$ and $B$. The solution of $A$ gives a white precipitate with $AgNO_3$ solution and the solution of $B$ gives a white precipitate with $BaCl_2$ solution. The type of isomerism exhibited by the complex is,

Which of the following aquated metal ions has the highest paramagnetism?

The magnetic moments of the complexes given below are in the order:
$I. [Ni(CO)_4]$
$II. [Mn(CN)_6]^{4-}$
$III. [Cr(NH_3)_6]^{3+}$
$IV. [CoF_6]^{3-}$