Which of the following must be documented in an "Officer's Operation Log"?

The requirement for documenting details regarding any incidents or abnormalities in an "Officer's Operation Log" is crucial because this log serves as an official record of daily operations and events that occur during a shift. Keeping a thorough account of incidents helps ensure accountability and provides valuable information for future reference or investigations. This documentation is essential for maintaining a clear history of the security operations, which can be crucial in analyses, legal matters, or reviewing performance and safety protocols.

The other options, while important in their own contexts, do not fall under the primary purpose of an Officer's Operation Log. Personnel changes might be recorded but are not the focus of incident documentation. Budget adjustments and construction project timelines are managed through different channels in an organization and do not pertain to the immediate operational activities or incidents encountered by security personnel. Thus, the specific emphasis on incidents and abnormalities aligns with the log's goal of ensuring a comprehensive overview of the security environment.