Which signal property is affected by modulation?

Modulation is a process used to encode information onto a carrier signal, which can involve changing different properties of that signal. One of the key aspects affected by modulation is amplitude. When a signal is modulated, the amplitude can vary in accordance with the information being sent. For instance, in amplitude modulation (AM), the strength of the carrier signal (its amplitude) changes in relation to the amplitude of the input signal (the audio or data signal).

While modulation can also lead to changes in frequency and wavelength due to the overall changes in the signal, the direct and intentional alteration of amplitude is what defines amplitude modulation. This modulation is crucial for transmitting data effectively over various media, ensuring that it can be accurately interpreted by receivers.

The other signal properties, such as frequency and wavelength, can also be influenced during modulation, especially in frequency modulation (FM); however, the ability to control amplitude to encode information directly highlights why amplitude is the most straightforward answer in this context. Clarity is not a signal property in the technical sense like amplitude is, making it an inappropriate choice as the correct answer.