Which of the following complexes exhibits optical isomerism?

The magnetic moment of $Cr(CO)_6$ is .....

Magnetic moment is expressed in

Select the correct code of $TRUE$ and $FALSE$ for the given statements:
$(a)$ Peroxide ion as well as dioxygen molecule both are paramagnetic species.
$(b)$ In the set of isomers,$[Cr(H_2O)_6]Cl_3$ and $[CrCl(H_2O)_5]Cl_2 \cdot H_2O$,both compounds can easily lose water molecules on treatment with conc. $H_2SO_4$.
$(c)$ During the transformation $NO \to NO^+$,bond length decreases and magnetic behavior changes from paramagnetic to diamagnetic.
$(d)$ An ether is more volatile than an alcohol,both having the same molecular formula.

Select the correct code regarding the total number of stereoisomers for the following compounds:
$I. [Ma_3b_2c]^{n \pm}, II. [M(AB)_3]^{n \pm}, III. [Ma_2b_2c_2]^{n \pm}$
$I - II - III$

Coordination isomerism is formed by the interchange of ligands between which of the following?