What part of the North American numbering plan is designated for emergency services?

In the North American numbering plan, 9-1-1 is the designated number for emergency services. This number is universally recognized as the emergency contact number for police, fire, and medical assistance. When someone dials 9-1-1, they are typically connected to trained emergency operators who can quickly dispatch the necessary services to the location of the call.

The other options signify different services: 8-1-1 is used for calling utility companies to check for underground lines before digging, 7-1-1 is a relay service for individuals who are deaf or hard of hearing to communicate with standard telephone users, and 6-1-1 is generally used for customer service inquiries with telephone service providers. Thus, 9-1-1 stands out specifically for its role in emergencies, making it the correct answer.