Final answer:
B. Tone generator and probe. The best tool for finding and labeling where a network connection terminates in a patch panel is a tone generator and probe. Ethernet cable testers, RJ-45 loopback plugs, and patch panel punchdown tools serve different purposes and would not be as effective for this specific task.
Step-by-step explanation:
A technician tasked with finding and labeling where a network connection terminates in a patch panel would be best served by using a tone generator and probe. A tone generator sends a signal down the wire, and with the help of the probe, the technician can scan the patch panel to locate the corresponding signal, thus identifying the termination point of the connection. The tone generator and probe are effective for tracing wires and locating breaks or shorts in cables as well.
An Ethernet cable tester is used to test the integrity of the data transmission in the cable itself, ensuring that the wires within the cable are functioning correctly. It can't specifically locate the termination point on a patch panel.
An RJ-45 loopback plug is a diagnostic tool used for testing network devices and can determine whether the port is functioning properly but is not designed to trace cables in a patch panel.
The patch panel punchdown tool is used to install wires into a patch panel but not to trace where a specific cable terminates.