Limiting and clamping circuits are commonly used in various electronic devices and systems for different purposes. Let's discuss each option mentioned in the question and understand how limiting and clamping circuits are employed in those applications:

a) FM Transmitters:
In FM (Frequency Modulation) transmitters, limiting circuits are used to ensure that the transmitted signal remains within a specific range. The purpose of the limiting circuit is to prevent over-modulation, where the amplitude of the modulated signal exceeds the maximum allowed limit. By limiting the amplitude, the transmitted FM signal can be kept within the specified limits, avoiding distortion and interference.

b) Television Receivers and Transmitters:
In television receivers and transmitters, both limiting and clamping circuits are employed. The limiting circuit ensures that the video signal remains within a certain amplitude range, preventing over-amplification or distortion. This helps in maintaining a consistent and high-quality display on the television screen.

On the other hand, clamping circuits are used to establish a reference voltage level for the video signal. This reference level is necessary for proper synchronization and accurate representation of black levels in the video signal. The clamping circuit shifts the entire waveform by a fixed amount so that the darkest parts of the video signal align with the reference voltage level.

c) Production of Various Signal Waveforms:
Limiting and clamping circuits are extensively used in the production of various signal waveforms, such as trapezoidal, square, or rectangular waves. These circuits help in shaping and controlling the amplitude of the waveform. Limiting circuits ensure that the waveform remains within a specified range, while clamping circuits establish the desired reference level for the waveform.

By employing these circuits, different waveforms can be generated accurately and reliably, which find applications in signal processing, communication systems, and waveform synthesis.

d) All of the Mentioned:
As discussed above, limiting and clamping circuits are employed in FM transmitters, television receivers and transmitters, and the production of various signal waveforms. Therefore, the correct answer is option 'D' - all of the mentioned.

In summary, limiting and clamping circuits play a crucial role in various electronic devices and systems. They ensure signal integrity, prevent distortion, establish reference levels, and shape waveforms accurately. These circuits are essential for reliable and efficient operation in applications such as FM transmitters, television systems, and waveform generation.