A marketing manager finds a person in the Database whose Marketing Qualified date has changed. The manager needs to identify the source and reason for the value change. Where can this information be accessed?

The Person Activity Log in Adobe Marketo Engage is the designated audit trail for an individual record. It captures a chronological history of all interactions and data modifications. When a field value like 'Marketing Qualified Date' changes, a "Data Value Changed" activity is logged. This entry specifies the field that was altered, its previous and new values, the timestamp of the change, and the source or reason (e.g., 'Smart Campaign', 'API', 'List Import'), directly answering the manager's query.

B. In a report: Reports are designed for data aggregation and trend analysis across many records, not for investigating the specific cause of a single data point change on an individual's record.
C. In a Smart List: A Smart List is a segmentation tool. While it can identify people whose data has changed, it does not provide the historical context or the specific source of that change for an individual.

1. Adobe Experience League - View a Person's Activity Log: "The Activity Log tab on a person’s detail page shows you a person’s entire history... This includes activities like Data Value Changed, which shows when a field’s value was updated and by what." (Marketo Engage Documentation, Core Marketo Concepts > People and Companies).

2. Adobe Experience League - Activity Type Glossary: The glossary defines the "Data Value Changed" activity. The details for this activity type include attributes such as Source Type (e.g., Smart Campaign, Form Fill Out, Web Service API) and Reason, which provides the specific cause for the change. (Marketo Engage Documentation, Core Marketo Concepts > Activities).