The interrogative hamza (أ) can ask whether a whole predication is true. This is confirmation-seeking (طلب التصديق). The questioner understands Zayd and the action of standing but seeks to establish whether that relation actually holds.
«أَقَامَ زَيْدٌ؟»
Did Zayd stand up?
The direct response is “Yes, he did” or “No, he did not.” One must distinguish grasping the proposition from knowing its truth. A person may understand the complete wording and still ask for confirmation of its actual occurrence.