Concept:The specific dhikr (supplication) recited while bowing in Ruku during Salah is the Sunnah taught by Prophet Muhammad (peace be upon him).
Explanation:In Ruku, the worshipper bows down and praises Allah with the words "Subhana Rabbiyal 'Azim", meaning "Glory is to my Lord, the Almighty".
This supplication is usually repeated at least three times while in the bowing posture.
Option A, "Subhana Rabiyal-A'la", is the supplication recited during Sujud (prostration), not Ruku.
Options B and C are not the prescribed dhikr for the Ruku posture.
Therefore, the correct choice is the one that mentions "Subhana Rabbiyal Azim".
Answer:D. Subhana Rabbiyal Azim