What is the usable radio frequency range mentioned in the text?

The usable radio frequency range is correctly identified as 10 kHz to 100 GHz. This range encompasses a broad spectrum of frequencies utilized for various communication applications, including AM and FM radio, television broadcasting, cellular networks, and Wi-Fi communications, among others.

The lower end of this range, starting from 10 kHz, allows for long-range communication, while the upper end at 100 GHz supports high-frequency applications like microwave transmission and advanced wireless technologies. By covering such a wide spectrum, this range includes multiple bands that are integral to different technologies and standards used across the information systems and telecommunications fields.

The other ranges mentioned don’t encompass this full spectrum; for example, 3-30 MHz and 30-300 MHz are much narrower and limit the applications to lower-frequency radio communications, while 3-30 GHz does not cover the lower frequencies which are critical for many applications.