A test involves synchronizing data from three separate data acquisition systems to correlate events accurately. As the Test Conductor, what is the most critical element to verify before the test begins to ensure data integrity?

1. That the data from all systems is being displayed on a single monitor for easy viewing.
2. That all systems are synchronized to a common, reliable time source (e.g., NTP or GPS).
3. That the operators for each system have open communication channels.
4. That each system has sufficient disk space to store the generated data logs.