Which of the following complexes is used as an anticancer agent?

In a complexometric titration of a metal ion with a ligand,the reaction is $M$ $(Metal-ion)$ + $L$ $(Ligand)$ $\to$ $C$ $(Complex)$. The end point is estimated spectrophotometrically (through light absorption). If '$M$' and '$C$' do not absorb light and only '$L$' absorbs,then the titration plot between absorbed light $(A)$ versus the volume of ligand '$L$' $(V)$ would look like:

Sodium thiosulphate $(Na_2S_2O_3 \cdot 5H_2O)$ is used in photography to

The mismatched combinations are
$A.$ Chlorophyll $- Co$
$B.$ Water hardness $- EDTA$
$C.$ Photography $- [Ag(CN)_2]^-$
$D.$ Wilkinson catalyst $- [(Ph_3P)_3RhCl]$
$E.$ Chelating ligand $- D^{-}$\text{Penicillamine}
Choose the correct answer from the options given below:

Schweitzer's reagent,used for dissolving cellulose in the manufacture of artificial silk,is

$A$ solution of $FeCl_3$ when treated with $K_4[Fe(CN)_6]$ gives a Prussian blue precipitate due to the formation of: