The correct answer is option 'B' - a resistor and capacitor in series.

Explanation:
An RC network, also known as an RC circuit or a resistor-capacitor circuit, is a combination of a resistor (R) and a capacitor (C) connected in series. This type of network is commonly used in electrical and electronic circuits for various applications.

1. Basic Structure:
- In an RC network, the resistor and capacitor are connected in series, which means that the current flowing through both components is the same.
- The resistor is a passive component that restricts the flow of electric current. It is represented by the symbol 'R' and is measured in ohms (Ω).
- The capacitor is an electronic component that stores electrical energy in the form of an electric field. It is represented by the symbol 'C' and is measured in farads (F).

2. Working Principle:
- When a voltage is applied across the RC network, the capacitor starts to charge or discharge depending on the polarity of the voltage source.
- Initially, when the voltage is applied, the capacitor behaves as an open circuit, and the current is limited by the resistor.
- As time passes, the capacitor charges up and allows more current to flow through the circuit, while the resistor limits the rate of charging.
- The charging process follows an exponential curve, and the time it takes for the capacitor to charge or discharge is determined by the RC time constant, which is given by the product of the resistance and capacitance values (RC).

3. Applications:
- RC networks are commonly used in timing circuits, oscillators, filters, and signal conditioning circuits.
- In timing circuits, the RC time constant is used to control the timing characteristics and determine the time delay.
- In oscillators, the RC network is used to provide frequency stability and control the oscillation frequency.
- In filters, the RC network is used to attenuate or pass certain frequencies depending on the values of the resistor and capacitor.

Overall, an RC network consisting of a resistor and capacitor connected in series is a fundamental circuit element used in various electrical and electronic applications. It allows for the control of timing, frequency, and filtering characteristics within a circuit.