Concept:Surah Ad-Duha mentions an oath by the morning brightness and another by the night.Explanation:The verse referred to is the second verse of Surah Ad-Duha (93:2).Its Arabic text is "Wal-layli iza saja".This means: "And by the night when it is still" or "when it grows dark".Nightfall describes the beginning of the night and its stillness.So the verse points to nightfall, not sunshine or daybreak.Answer:D. Nightfall