Introduction:
A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a three-terminal device that can be used as a voltage-controlled switch or as an amplifier. In order to understand in which configuration a MOSFET works as an amplifier, let's discuss the three common configurations: Common Source (CS), Common Gate (CG), and Common Drain (CD).

Common Source (CS) Configuration:
In the Common Source configuration, the input signal is applied to the Gate terminal, while the output is taken from the Drain terminal. The Source terminal is common to both input and output. In this configuration, the MOSFET works as an amplifier. The input voltage controls the output current, allowing amplification of the input signal. The voltage gain in this configuration is relatively high, making it suitable for amplification applications.

Common Gate (CG) Configuration:
In the Common Gate configuration, the input signal is applied to the Source terminal, while the output is taken from the Drain terminal. The Gate terminal is common to both input and output. In this configuration, the MOSFET works mainly as a voltage buffer rather than an amplifier. The input voltage controls the output voltage, but the current gain is low. Therefore, it is not typically used as an amplifier.

Common Drain (CD) Configuration:
In the Common Drain configuration, the input signal is applied to the Gate terminal, while the output is taken from the Source terminal. The Drain terminal is common to both input and output. In this configuration, the MOSFET also works as an amplifier. The input voltage controls the output current, allowing amplification of the input signal. The voltage gain in this configuration is relatively low, but it provides high current gain and impedance matching.

Conclusion:
In summary, a MOSFET works as an amplifier in both the Common Source (CS) and Common Drain (CD) configurations. The Common Gate (CG) configuration is mainly used as a voltage buffer rather than an amplifier. Therefore, the correct answer is option 'D' - All of the mentioned.

Bcs it ha 3 terminal source gate drain and it is voltage controlled device