Answer

Correct option: (i) One resistor and one capacitor

Explanation

A basic first-order RC filter is made using one resistor and one capacitor. It has one energy-storage element and therefore has a roll-off of approximately 20 dB/decade beyond its cutoff frequency.

For a simple RC low-pass filter, the cutoff frequency is:

$$f_c = \frac{1}{2\pi RC}$$

Below the cutoff frequency, the signal passes with relatively little attenuation. Above the cutoff frequency, higher-frequency components are increasingly attenuated.

Therefore, the correct answer is (i).