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
When the cause of death is not clear even after entire examination on autopsy, what it is called? 
Select and explain. 
A. Defective autopsy, B. Normal autopsy, C. Obscure autopsy, D. Negative autopsy
D: Negative autopsy
Answer: D: Negative autopsy 
Explanation: Ans. is 'd' i.e., Negative autopsy