Which analysis best fits the second clause in «مَرِضَ زَيْدٌ. أَضْنَاهُ السَّهَرُ»?

Supplementary Practice 1: Applied Analysis of Faṣl, Waṣl, Ījāz and Iṭnāb

• Complete disjunction with no contextual relation
• An explanatory resumption answering an implied question about the cause
• Word-level syntactic apposition
• A position requiring circumstantial wāw