Most of the gain and selectivity in a superhet is obtained in thea.Mixerb.AF amplifierc.IF amplifierd.RF amplifier

The most gain and selectivity in a superheterodyne receiver is obtained in the IF (Intermediate Frequency) amplifier. So, the correct answer is c. IF amplifier.

Here's why:

1. Mixer: The mixer in a superheterodyne receiver is used to convert the incoming RF signal to an IF signal. It doesn't provide significant gain or selectivity.

2. AF Amplifier: The AF (Audio Frequency) amplifier is used to amplify the demodulated audio signal. While it does provide gain, it doesn't contribute to selectivity.

3. IF Amplifier: The IF amplifier amplifies the IF signal and is where most of the gain and selectivity in a superheterodyne receiver is achieved. The IF stage has a fixed frequency, which allows for high gain and selectivity.

4. RF Amplifier: The RF (Radio Frequency) amplifier is used to amplify the incoming RF signal before it is mixed down to the IF. While it does provide some gain, it doesn't contribute significantly to selectivity.