Chlorophyll is a

The reagent used for the detection of $Ni^{2+}$ is $A$. $x$ moles of $A$ react with $Ni^{2+}$ to form a complex of $C$ color. $A$,$x$,and $C$ are respectively:

Hemoglobin is a complex of which ion?

To inhibit the growth of tumours,identify the compounds used from the following:
$(A)$ $EDTA$
$(B)$ Coordination Compounds of $Pt$
$(C)$ $D$-Penicillamine
$(D)$ $Cis-Platin$
Choose the correct answer from the option given below:

$A$ white precipitate of $AgCl$ dissolves in excess of
$(I)$ $NH_{3(aq)}$
$(II)$ $Na_2S_2O_3$
$(III)$ $NaCN$

Which ligand is useful for the removal of the toxic effect of lead metal in the body during chelate therapy treatment?