Modulation is done in

Options

A. Transmitter
B. Radio receiver
C. Communication channel
D. None of these

Answer

### Step-by-Step Solution:

1. **Understanding Modulation**:
- Modulation is the process of modifying a carrier wave by superimposing an information signal (like audio) onto it. This allows the signal to be transmitted over long distances.

2. **Role of Carrier Wave**:
- The carrier wave is a high-frequency wave that carries the information signal. By modulating the carrier wave, the frequency of the transmitted signal is increased, making it suitable for transmission through various media.

3. **Function of a Transmitter**:
- A transmitter is a device that converts the information signal into a form that can be transmitted through a communication channel. It prepares the modulated signal for transmission.

4. **Conclusion**:
- Since modulation is a key process in preparing the signal for transmission and is performed by the transmitter, we conclude that modulation is done in the transmitter.

5. **Final Answer**:
- Therefore, the correct answer to the question "Modulation is done in" is **Transmitter**.