Answer:
E° denotes the reduction potential of a particular element.
E° value of Sn2+ is higher than that of Cr3+ This means Sn2+ is able to undergo reduction more than Cr3+.So Sn2+ will undergo reduction while Cr(s) will get oxidised. This eliminates statement a.
Since the oxidation reaction Cr(s) ---> Cr3+ (aq) + 3e-
takes place, the concentration of Cr3+ ions will increase because more and more Chromium ions are added to solution. Therefore b is correct.
Mass of Sn metal will increase because Sn2+ ions get reduced to the Sn metal with time. So d is wrong.
Tin metal will form as in c but an electric current is not applied to the cell because the galvanic cell converts chemical energy into electrical energy and because of that an external current source is not needed.