When viewing or exporting event search results from the IBM QRadar Log Activity tab, the default columns are configured to provide a concise, high-level summary for an initial investigation. The columns listed in option A—Log Source, Event Count, High Level Category, and Related Offense—are fundamental to this initial analysis. Log Source identifies the origin, Event Count shows the frequency (especially in grouped views), High Level Category classifies the event type, and the Related Offense column indicates if the event is correlated into a security offense. While the complete default view includes other columns, this combination represents the most accurate and functionally relevant set among the choices.

B. 'Application' and 'Username' are not default columns. They are valuable for specific investigations but must be manually added to the view as they are not universally present in all log types.

C. 'Username' and 'Source Port' are not part of the default column set. These are specific event properties that an administrator would typically add for a more granular investigation.

D. 'Protocol', 'Storage Time', 'Destination Port', and 'Source Port' are all non-default columns that provide specific network or metadata details and are not included in the default summary view.

1. IBM QRadar SIEM User Guide (Version 7.5.0), Chapter 6: "Investigating events", Section: "Event investigation columns", Page 62. This section details the columns available in the Log Activity tab, noting that the default display includes columns "commonly used for event investigations," such as Log Source, Event Count, and category information. The presence of an offense indicator is also a standard UI element.

2. IBM Security Learning Academy, Course BQ103G: IBM QRadar SIEM Foundations, Unit 5: "Investigating an Offense Triggered by Events". The lab exercises and user interface demonstrations in this official course consistently show Log Source, Event Count, and Category information as primary columns in the default Log Activity view. The link between events and offenses is a core concept, making the Related Offense information a key default element.