Final answer:
Angela should use a file integrity checking tool to be notified of changes to her server's important configuration files. This type of control actively monitors file changes and notifies the administrator accordingly.
Step-by-step explanation:
Angela is looking for a control to notify her of changes made to important configuration files on her server. Out of the options provided, the best fit for this requirement is C. File integrity checking. This tool scans the configuration files and computes a checksum or a hash value, which it compares during every scan to detect any changes. If any alteration is detected, the system can be configured to notify the server administrator, in this case, Angela.
Configuration management tools are also related, but they focus more on maintaining the configurations as per a defined state rather than actively notifying about modifications. Anti-malware is essential for protection against malicious software and logging provides records of events which can include changes to files but may not actively notify administrators of changes.