Which among the following is used in the treatment of cancer?

Hemoglobin is a complex of which of the following?

When conc. $H_2SO_4$ is treated with $K_4[Fe(CN)_6]$,$CO$ gas is evolved. If dilute $H_2SO_4$ is used instead of conc. $H_2SO_4$,the gas evolved is:

The potassium ferrocyanide solution gives Prussian blue colour,when added to :

If a didentate ligand ethane-$1, 2$-diamine is progressively added in the molar ratio $en : Ni :: 1: 1, 2: 1, 3: 1$ to $[Ni(H_2O)_6]^{2+}$ aqueous solution,the following coordination entities are formed:
$I$. $[Ni(H_2O)_4en]^{2+}_{(aq)} -$ pale blue
$II$. $[Ni(H_2O)_2(en)_2]^{2+}_{(aq)} -$ blue/purple
$III$. $[Ni(en)_3]^{2+}_{(aq)} -$ violet
The wavelengths in $nm$ of light absorbed in the case of $I$ and $III$ are respectively:

Dimethyl glyoxime gives a red precipitate with $Ni^{2+}$,which is used for its detection. To get this precipitate readily,the best $pH$ range is