Step 1: Objective: Identify the constituent buildings of the ancient Nālandā Mahāvihāra (University) library.
Step 2: Analysis: The Nālandā library was named Dharma Gunj (Mountain of Truth). Historical records, notably from Tibetan sources like Taranatha, indicate it comprised three large, multi-storied structures. These were:
Ratnasāgara (Ocean of Jewels)
Ratnodadhi (Sea of Jewels)
Ratnarañjaka (Jewel-adorned)
These align with options (B), (D), and (C). Option (A), Ratnakirti, refers to a Buddhist scholar associated with Vikramaśīla University, not a Nālandā library building.
Step 3: Conclusion: The Nālandā library buildings were Ratnasāgara, Ratnarañjaka, and Ratnodadhi. The correct selection comprises options (B), (C), and (D).