What is the wāw at the beginning of al-ʿĀdiyāt 100:1?

Supplementary Practice 25 — Comparative Rhetoric of Sūrat az-Zalzalah and Sūrat al-ʿĀdiyāt

• An oath particle introducing the scene before its response
• A circumstantial wāw attached to an earlier subject
• A wāw of accompaniment requiring a concomitant object
• An opening wāw with no oath force