What is the coordination number of cobalt in $[Co(NH_3)_3Cl_3]$?

Which of the following are examples of double salts?
$A$. $FeSO_4 \cdot (NH_4)_2SO_4 \cdot 6H_2O$
$B$. $CuSO_4 \cdot 4NH_3 \cdot H_2O$
$C$. $K_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O$
$D$. $Fe(CN)_2 \cdot 4KCN$
Choose the correct answer.

Mohr's salt is

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

List-$I$ (Complex)	List-$II$ (Primary valency and Secondary valency)
$(A)$ $[Co(en)_2 Cl_2] Cl$	$(I)$ $3, 6$
$(B)$ $[Pt(NH_3)_2 Cl(NO_2)]$	$(II)$ $2, 4$
$(C)$ $Hg[Co(SCN)_4]$	$(III)$ $3, 4$
$(D)$ $[Mg(EDTA)]^{2-}$	$(IV)$ $2, 6$

Choose the correct answer from the options given below:

The ligands which can get attached to the central metal ion through more than one atom are called

Identify the anionic complex from the following.