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
The rare earth elements used in intensifying screens which emit green light are: 
Select and explain. 
A. Yttrium tantalite, niobium activated, B. Gadolinium oxysulfide, terbium activated, C. Yttrium tantalite, terbium activated, D. Gadolinium oxysulfide, niobium activated
B: Gadolinium oxysulfide, terbium activated
Answer: B: Gadolinium oxysulfide, terbium activated 
Explanation: None