To solve this problem, we need to understand the behavior of a capacitor in an AC circuit.$\\$The capacitive reactance $X_C$ is given by the formula:$\\ X_C = \frac{1}{2 \pi f C} \\$where $f$ is the frequency of the AC source and $C$ is the capacitance.$\\$• As the frequency $f$ decreases, the capacitive reactance $X_C$ increases.$\\$• Therefore, Option 1 is incorrect, and Option 4 is also incorrect.$\\$The displacement current $I_d$ in the capacitor is given by:$\\ I_d = V \cdot \omega C = V \cdot 2 \pi f C \\$where $V$ is the voltage across the capacitor.$\\$• As the frequency $f$ decreases, the displacement current $I_d$ decreases.$\\$• Therefore, Option 2 is incorrect, and Option 3 is correct.$\\$Thus, the correct answer is Option 3: Displacement current decreases.$\\$