Which statement accurately reflects the pronoun in wa-innahu ʿalā dhālika la-shahīd?

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

• It can only refer to the racing horses
• It must always be an impersonal pronoun with no antecedent
• There is no pronoun in the verse
• Recognized interpretations take it as referring either to the person or to God