Correct Answer - B
(b) In the metallurgy of aluminium , electrolysis is performed in a steel vessel with lining of carbon acts as cathode and graphite acts as anode. During this process graphite Chemical reaction to CO and `CO_(2)` .
`2Al_(2)O_(3) + 3C to 4Al + 3CO_(2)`
This process is known as Hall-Herolt process. The electrolytc reactions are
At cathode `Al^(3+)` (melt) `+3e^(-) to Al(l)`
At anode `C(s) + O^(2-)("melt") to CO(g) +2e^(-)`
`" "C(s)+2O^(2-) ("melt") to CO_(2)(g) +4e^(-)`