When must an institution collect additional information regarding a student's prior enrollment?

The correct answer is based on the significance of the Unusual Enrollment History (UEH) flag, which highlights a student's prior enrollment patterns and can raise concerns regarding their eligibility for federal financial aid. When the UEH flag indicates questionable enrollment, it suggests that there may be discrepancies or issues in the student's past academic history that require further investigation. In this context, institutions are required to gather additional information to verify the student's enrollment history. This may include transcripts or details about the institutions the student attended, and a review of whether the student earned credits or completed the courses for which they received financial aid.

The other options do not align with the specific regulations concerning the UEH flag. A student's request for information does not trigger an institution’s obligation to collect additional enrollment data. Similarly, changing majors or graduation does not typically warrant a review of enrollment history unless explicitly tied to the UEH flag concerns. Thus, the necessity to gather additional information arises specifically in circumstances where there are uncertainties related to the student's enrollment that have been flagged by the UEH system.