*Question T7A04:
Which term describes the ability of a receiver to discriminate between multiple signals?*  

*Correct Answer is  C: Selectivity*  

### AI Response: (may contain errors)  

The correct answer to the question is **Selectivity**.

1. **Why Selectivity is Correct:**
   - Selectivity refers to a receiver's ability to isolate and receive a specific signal while rejecting other signals that are close in frequency. This is crucial in crowded frequency bands where multiple signals may be present. A highly selective receiver can effectively differentiate between these signals, allowing for clearer communication.

2. **Why the Other Choices are Incorrect:**
   - **A: Discrimination ratio**: This term is not commonly used in the context of receiver performance. It may refer to the ability to distinguish between signals, but it is not the standard term for the ability to reject unwanted signals.
   - **B: Sensitivity**: Sensitivity measures how well a receiver can detect weak signals. While sensitivity is important for receiving signals, it does not address the ability to discriminate between multiple signals.
   - **D: Harmonic distortion**: This refers to the distortion that occurs when a signal is altered in a way that introduces harmonics (multiples of the original frequency). It is not related to the ability to discriminate between signals.

3. **Useful Concepts:**
   - Selectivity is often quantified in terms of bandwidth. A narrower bandwidth typically indicates higher selectivity, as it allows the receiver to focus on a smaller range of frequencies.
   - A common rule of thumb is that a receiver should have a selectivity that is at least 10 times the bandwidth of the desired signal to effectively reject adjacent signals.

In summary, selectivity is the key term that describes a receiver's ability to discriminate between multiple signals, making it the correct answer for this question.