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
To restrict X-ray beam which of the following is done: 
Select and explain. 
A. Collimation of beam, B. Increase Kvp, C. Decrease target object distance, D. Use a grid
A: Collimation of beam
Answer: A: Collimation of beam 
Explanation: None