وَمَا تِلْكَ بِيَمِينِكَ يَا مُوسَى
What is that in your right hand, Moses?
This question is not explained by a need to acquire previously unknown information. In rhetorical context, the known is posed as a question to direct attention, prepare discourse, or achieve another purpose; that is the operative distinction in tajāhul al-ʿārif.
Not every interrogative belongs to this figure. If the questioner genuinely seeks unknown information, it is an ordinary question. Context determines the function.