The standard reduction potentials at 298 K for single electrodes are given below:
Electrode
Electrode Potential (volt)
$\mathrm{Mg}^{2+}/\mathrm{Mg}$
-2.34
$\mathrm{Zn}^{2+}/\mathrm{Zn}$
-0.76
$\mathrm{Zn}^{2+}/\mathrm{Fe}$
-0.44
From this we can infer that
(a)Zn can reduce both $\mathrm{Mg}^{2+}$ and $\mathrm{Fe}^{2+}$
(b)Fe can reduce both $\mathrm{Mg}^{2+}$ and $\mathrm{Zn}^{2+}$
(c)Mg can reduce both $\mathrm{Zn}^{2+}$ and $\mathrm{Fe}^{2+}$
(d)Mg can reduce $\mathrm{Zn}^{2+}$ but not $\mathrm{Fe}^{2+}$
Answer
Answer: C ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
The most negative couple (Mg²⁺/Mg, −2.34 V) is the strongest reducing agent, so Mg reduces both Zn²⁺ (−0.76 V) and Fe²⁺ (−0.44 V); Zn cannot reduce Mg²⁺ (c).