«أَلَمْ نَشْرَحْ لَكَ صَدْرَكَ»
Have We not expanded your breast for you?
The hamzah marks interrogation, while lam negates and makes the present verb jussive. Nashraḥ is jussive and ṣadraka is its direct object. The form is interrogative, but the context recalls an established favor rather than seeking previously unknown information.
Its rhetorical work is affirmative prompting and reminder (taqrīr). A question mark alone cannot determine that a sentence asks for new information.