Which of the following graphs most appropriately represents a zero order reaction?

Identify the coordination complexes in which the central metal ion has $\mathrm{d}^4$ configuration.

(A) $\left[\mathrm{FeO}_4\right]^{2-}$

(B) $\quad\left[\mathrm{Mn}(\mathrm{CN})_6\right]^{3-}$

(C) $\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}$

(D) (E) $\left[\mathrm{NiF}_6\right]^{2-}$

Choose the correct answer from the options given below :

Identify A, B and C in the given below reaction sequence

Standard electrode potentials for a few half cells are mentioned below :

$$\begin{aligned} & \mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.34 \mathrm{~V}, \mathrm{E}_{\mathrm{Zn}^{2+} / \mathrm{Zn}}^{\circ}=-0.76 \mathrm{~V} \\ & \mathrm{E}_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=0.80 \mathrm{~V}, \mathrm{E}_{\mathrm{Mg}^{2+} / \mathrm{Mg}}^{\circ}=-2.37 \mathrm{~V} \end{aligned}$$

Which one of the following cells gives the most negative value of $\Delta \mathrm{G}^{\circ}$ ?