This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fundamentals in Radiology, Subject name: Radiology
X-ray Aifact is - 
Select and explain. 
A. A radiolucent area, B. Any abnormal opacity in the radiograph, C. Produced when patient moves while taking the shoot, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Common aifacts (all forms of radiography) motion aifact due to patient movement resulting in a distoed image image compositing (or twin/double exposure) superimposition of two structures from different locations due to double exposure of same film/plate radiopaque objects on/external to the patient (e.g. debris in the housing debris in the housing caused by the collimator tube can cause small trapezoidal regions, indicative of lead shavings