What is the name of the service that is authorized to share a portion of the ISM band?

The correct choice identifies the Amateur Radio Service as the authorized service that can share a portion of the Industrial, Scientific, and Medical (ISM) band. The ISM bands are specific radio frequency bands that are allocated for the use of industrial, scientific, and medical equipment rather than for communications. However, amateur radio operators have been granted the ability to use certain frequencies within these bands, specifically for non-commercial, hobbyist purposes.

Amateur radio operators must adhere to regulations set by national and international authorities, ensuring that their activities do not interfere with the primary users of the ISM band. This service encourages experimentation and communication among individuals, promoting technical skill development and public service.

Other choices refer to different types of services that do not typically engage with the ISM bands in the same capacity or under similar regulations. For instance, public service bands are used for emergency communications but are distinct from amateur radio activities. Commercial broadcasting is focused on the transmission of entertainment and information for profit, while national security service encompasses governmental communication for defense, which operates under separate regulatory frameworks. These services do not participate in the sharing of the ISM band in the same way amateur radio does.