Final answer:
Observing conditions is the most probable source of the item of physical information in the working papers during a fraud investigation.
Step-by-step explanation:
The most probable source of the item of physical information contained in the working papers during a fraud investigation is observing conditions.
When conducting a fraud investigation, it is important for the internal auditor to observe the physical conditions or elements related to the fraud. This can include observing the physical state of assets, the condition of documents or records, or any other physical evidence that may provide insights into the fraud.
By observing conditions, the internal auditor can gather firsthand information that can be documented and analyzed as part of the investigation process.