وَمَا هُوَ عَلَى ٱلْغَيْبِ بِضَنِينٍ ۝٢٤ Why is ضَنِينٍ genitive in form?

Surah At-Takwir — Part 4

• Because it is an adjective
• Because of the emphatic extra bāʾ
• Because it is a subject
• Because it follows an iḍāfa