Which analysis correctly describes fa-sabbiḥ?

Supplementary Practice 22: Comparative Rhetorical Study of Sūrat al-Kāfirūn and al-Naṣr

• Fāʾ marks an oath and sabbiḥ is past
• Fāʾ is categorical negation and sabbiḥ a nominal predicate
• Fāʾ links the response to idhā and sabbiḥ is an imperative
• Fāʾ is circumstantial wāw and sabbiḥ is genitive