The correct answer is: D. L and C.
A resonant circuit is an electrical circuit that is designed to resonate at a specific frequency. This is done by combining inductors (L) and capacitors (C) in a specific way. When the circuit is resonated, it will have a high impedance at that frequency and a low impedance at all other frequencies. This makes it useful for filtering signals and for creating oscillators.
Option A is incorrect because it includes resistors (R). Resistors are not necessary for a circuit to resonate.
Option B is incorrect because it includes resistors (R) and capacitors (C). However, it does not include inductors (L). Inductors are necessary for a circuit to resonate.
Option C is incorrect because it includes only resistors (R). Resistors are not necessary for a circuit to resonate.
Option D is the correct answer because it includes inductors (L) and capacitors (C). Inductors and capacitors are necessary for a circuit to resonate.