With the hamza, bringing an agent or object to the front can shift what the question focuses on. Is the uncertainty about the actor, the affected person, or the event itself? Word order provides an important clue.
«أَأَنْتَ ضَرَبْتَ زَيْدًا؟»
Was it you who struck Zayd?
«أَزَيْدًا ضَرَبْتَ؟»
Was Zayd the one whom you struck?
The first can foreground the agent; the second can foreground the object. Yet context still determines the live alternatives. A sound analysis states what answer the speaker is actually seeking, not merely the syntactic labels of the words.