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: Radiology
[{'content': 'The rare earth elements used in intensifying screens which emit green light are: \nSelect and explain. \nA. Yttrium tantalite, niobium activated, B. Gadolinium oxysulfide, terbium activated, C. Yttrium tantalite, terbium activated, D. Gadolinium oxysulfide, niobium activated', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]