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.