The ability of a receiver to separate one signal from others on closely adjacent frequencies is called thea.Selectivityb.Sensitivityc.S/N ratiod.Gain

To determine the correct answer to the question, let's analyze the options provided in detail:

1. Selectivity: This term refers to the ability of a receiver to distinguish between different signals that are close in frequency. This means that selectivity measures how well a receiver can tune into a specific frequency while rejecting others that are nearby.

2. Sensitivity: Sensitivity is the ability of a receiver to detect weak signals. While it is important in receiving signals, it does not specifically relate to separating signals of closely adjacent frequencies.

3. S/N ratio (Signal-to-Noise Ratio): The S/N ratio refers to the level of a desired signal relative to the level of background noise. It is more about the quality of the signal rather than the ability to separate signals on close frequencies.

4. Gain: Gain refers to the ability of an amplifier to increase the power of a signal. It does not pertain to the separation of signals.

Final Answer

The correct answer is a. Selectivity. Selectivity is the ability of a receiver to separate one signal from others on closely adjacent frequencies.