This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Bismuth Oxide incorporated in MTA results in grey discolouration of crown. In newer material this Bismuth Oxide is replaced with? 
Select and explain. 
A. Terbium-Dysisopropium, B. Tantalam Oxide, C. Bismuth Carbonate, D. Titanium Oxide
B: Tantalam Oxide
Answer: B: Tantalam Oxide 
Explanation: None