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: Forensic Medicine
Ideal tissue for diatom study: 
Select and explain. 
A. Bone marrow of femur, B. Lung, C. Liver, D. All
A: Bone marrow of femur
Answer: A: Bone marrow of femur 
Explanation: A i.e. Bone marrow of femur