From the given table, identify the set of metals cannot be obtained by carbon reduction.
Set - A
The metals like K, Na, Mg, Ca, Al lie at the top of the reactivity series and are highly reactive in nature and hence cannot be obtained by using carbon reduction process.
The metals like Zn, Fe, Pb lie in the middle of the reactivity series are moderately reactive. The metals like Cu, Au, Ag, Pt lying at the bottom of the reactivity series are least reactive and are found in their free states. These can be obtained by using carbon reduction process.