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
Filters of which metal that is used to remove long wave
length X-rays from the primary beam is: 
Select and explain. 
A. Platinum, B. Aluminium, C. Copper, D. Lead
B: Aluminium
Answer: B: Aluminium 
Explanation: None