What does modulation primarily involve?

Modulation primarily involves varying properties of waveforms to encode information. This process is essential in communications, where information such as voice, video, or data needs to be transmitted over various transmission media, including air, cables, or fiber optics. By altering characteristics of a waveform—such as its amplitude, frequency, or phase—modulation allows the original information to be superimposed onto the waveform, making it suitable for transmission.

This technique is fundamental in various communication technologies, including radio broadcasting, television, and internet data transmission, as it effectively enables the transfer of information across different channels without interference. The other options do not encapsulate the essence of modulation; while changing physical connections and managing network routing relate to networking, and distributing cryptographic keys pertains to security, they do not describe the mechanism of encoding information into waveforms that characterizes modulation.