Which statement about Event Viewer is true?

The correct statement about Event Viewer is that it can be used to help identify the root cause of why some calls failed. Event Viewer is a tool that logs events within the system, including warnings, errors, and informational messages that can indicate issues within the call handling process.

When analyzing call failures, Event Viewer provides vital information such as error codes, timestamps, and details about the context in which the failure occurred. This data can help administrators trace back through the sequence of events leading to a call's failure, making it easier to diagnose problems related to system configuration, connectivity, or other components involved in the call process.

While other options mention aspects of Event Viewer, they do not accurately capture its primary utility in troubleshooting call failures. The first option about identifying who made a configuration change is more pertinent to a change management tool rather than Event Viewer specifically. Tracking system performance is just a portion of what Event Viewer can do, making the notion that it is limited to performance tracking incorrect. Finally, the claim that Event Viewer cannot be used for troubleshooting issues overlooks its fundamental purpose of logging events that are crucial for diagnosing problems.