Ferric oxide in blast furnace's upper half is mainly reduced by:

\(CO\)

The correct answer is option 1. \(CO\).

In the upper half of the blast furnace, where the temperature is relatively lower compared to the lower sections, the reduction of iron oxides primarily occurs through the reaction with carbon monoxide (\(CO\)).

The overall reduction process can be represented by the following equations:

\[Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2\]

\[Fe_3O_4 + 4CO \rightarrow 3Fe + 4CO_2\]

In these reactions, carbon monoxide (\(CO\)) acts as a reducing agent, reacting with iron oxides (\(Fe_2O_3\) and \(Fe_3O_4\)) to produce elemental iron (\(Fe\)) and carbon dioxide (\(CO_2\)).

So, the correct answer is: 1. \(CO\)