An indicator 'X' is used for studying the effect of variation in concentration of iodide on the rate of reaction of iodide ion with $$\mathrm{H_2O_2}$$ at room temp. The indicator 'X' forms blue coloured complex with compound 'A' present in the solution. The indicator 'X' and compound 'A' respectively are :

A chloride salt solution acidified with dil.HNO$$_3$$ gives a curdy white precipitate, [A], on addition of AgNO$$_3$$. [A] on treatment with NH$$_4$$OH gives a clear solution B. A and B are respectively :

Which one amongst the following are good oxidizing agents?

A. Sm$$^{2+}$$

B. Ce$$^{2+}$$

C. Ce$$^{4+}$$

D. Tb$$^{4+}$$

Choose the most appropriate answer from the options given below :

An ammoniacal metal salt solution gives a brilliant red precipitate on addition of dimethylglyoxime. The metal ion is :