When marking underground facilities

This choice is incomplete and does not specify what the symbol C designates. Without additional context, it fails to convey the essential information regarding abandoned facilities that the question seeks.

The symbol C does not indicate a restriction of access. Instead, it specifically marks the status of a facility as abandoned. Other symbols or markers might be used to denote restricted access, making this choice incorrect in the context of the question.

This choice misrepresents the purpose of the symbol C. The designation of an abandoned facility does not necessarily imply the absence of an Emergency Management System (EMS) marker. Therefore, this option does not accurately reflect the meaning of the symbol C.

The symbol C does not indicate the endpoint of a service line. Instead, it identifies an abandoned facility, which is a distinct and specific use of the symbol that does not relate to service line markers.