Final answer:
When adding a directory monitor, specifying a file extension applies to all files within the directory and its subdirectories, which is essential for data integrity and monitoring by backup software.
Correct option is 1) file extension
Step-by-step explanation:
When you add a directory monitor and specify a file extension explicitly, it applies to all files in the directory and subdirectories. This means that the directory monitoring software will track changes, such as creations, modifications, or deletions, for all files that match the specified extension, ensuring that files like '.txt', , etc., are monitored if specified. Directory monitors are usually part of a file management system or backup software, helping to maintain the integrity of data by keeping a watchful eye on important files and alerting users to recent changes.
This proactive approach helps in data management, version control, and timely response to modifications or updates within the monitored directory.