For the cell, Mg | Mg2+ || Cu2+ | Cu

a.  Mg acts as cathode

b.  Cu acts as cathode

c.  The cell reaction is   \(Mg + Cu^{2+} \rightarrow Mg^{2+} + Cu\)

d.  Cu is the oxidising agent

The correct choice among the given is: 

1. (a, b) 2. (b, c)
3. (c, d) 4. (a, d)
Left side of cell reaction represents oxidation half cell i.e., oxidation of Mg and right side of cell represents reduction half cell reactions i.e., reduction of copper.
(ii) Cu is reduced and reduction occurs at cathode.
(iii) Mg is oxidised and oxidation occurs at anode.
(iv) Whole cell reaction can be written as
Hence, options (b) and (c) both are correct choices.