Which of the following aspects is a challenge when handling test data for an AI-based...

The syllabus explicitly mentions challenges of handling personal data and ensuring privacy when testing AI-based systems:

"The management of personal data and sensitive data is often a concern during testing, as testing typically requires realistic data and it is difficult to fully anonymize data."

(Reference: ISTQB CT-AI Syllabus v1.0, Section 7.3, page 52 of 99)