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
Most radio dense substance is - 
Select and explain. 
A. Fluid, B. Soft tissue, C. Brain, D. Bone
D: Bone
Answer: D: Bone 
Explanation: Increasing order of radiodensity : AIR FAT WATER BONE METAL