What does selectivity refer to in a receiver?

Selectivity in a receiver pertains to its ability to distinguish between the desired signal and unwanted signals, such as noise or interference. A highly selective receiver will effectively filter out audio from other channels or frequencies, allowing the operator to clearly receive the intended communication. This characteristic is particularly crucial in environments where many signals may be present simultaneously, ensuring that the receiver can focus on the relevant signal without being overwhelmed by others.

In contrast, the other options address different functionalities that are not directly related to selectivity. Combining signals, amplifying all signals uniformly, or converting signal types are important aspects of signal processing but do not define the specific capability of filtering out unwanted signals, which is the essence of selectivity.