هَلْ رَأَيْتَ الْقَمَرَ؟
Did you see the moon?
أَتَدَّعِي أَنَّكَ رَأَيْتَ كُلَّ شَيْءٍ وَقَدْ حَجَبَتِ السُّحُبُ الْأُفُقَ؟
Do you claim to have seen everything when clouds obscured the horizon?
The first may be a straightforward request for information. In the second, the stated obstruction makes rhetorical denial plausible: the speaker challenges an exaggerated claim rather than simply soliciting a fact.
An interrogative particle alone does not prove an interrogative is rhetorical. Context and communicative purpose decide its force.