Then, initial Pressure will be,

\(P_{i}=\frac{n R T_{i}}{V_{i}}\) [From ideal gas law]

Now it final volume \(V_{f}=2 V_{i}\) and final temperature \(T_{f}=T_{i} / 2\).

Then final pressure will be,

\(P_{f} =\frac{n R T_{f}}{V_{f}}=\frac{n R\left(T_{i} / 2\right)}{\left(2 V_{i}\right)}\)

\(\Rightarrow P_{f} =\frac{1}{4} \frac{n R T_{i}}{V_{i}}\)

\(\Rightarrow P_{f} =\frac{1}{4} P_{i}\)

Thus, option \((C)\) is correct.