Blood haemoglobin contains the metal

$A$ reagent which gives a brilliant red precipitate with $Ni^{2+}$ ions in a basic medium is

In the complex ion $[Co(CN)_6]^{3-}$,the $Co^{3+}$ ion absorbs radiation of the violet color from the visible spectrum. What will be the color of its aqueous solution?

$A$ solution when treated with dimethyl glyoxime gives a rose red complex. The metal present is

The substance used in the treatment of cancer is ........

The $INCORRECT$ statement is: