Which complex cannot ionise in solution?

Arrange the ligands $NH_3, en, Cl^-,$ and $CO$ in the increasing order of their field strength (spectrochemical series).

The colour of cobalt chloride solution is:

Match List-$I$ (Molar Conductivity) with List-$II$ (Complex Formula) and select the correct option:

List-$I$ (Conductivity)	List-$II$ (Formula)
$A. \ 229$	$i. \ [Pt(NH_3)_3Cl_3]Cl$
$B. \ 97$	$ii. \ [Pt(NH_3)_4Cl_2]Cl_2$
$C. \ 404$	$iii. \ [Pt(NH_3)_5Cl]Cl_3$
$D. \ 523$	$iv. \ [Pt(NH_3)_6]Cl_4$

The complex having highest electrical conductivity in aqueous solution under similar conditions is . . . . . . .

The $IR$ stretching frequencies of free $CO$ and $CO$ in $[V(CO)_6]^-$,$[Cr(CO)_6]$ and $[Mn(CO)_6]^+$ are $2143 \, cm^{-1}$,$1860 \, cm^{-1}$,$2000 \, cm^{-1}$ and $2090 \, cm^{-1}$,respectively. Then the correct statement about metal carbonyls is: