This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Decreased protein lipid ratio seen in: 
Select and explain. 
A. Inner mitochondrial membrane, B. Outer mitochondrial membrane, C. Sarcoplasmic reticulum, D. Myelin sheath membrane
D: Myelin sheath membrane
Answer: D: Myelin sheath membrane 
Explanation: Nerve cell membrane with myelin sheath are rich in lipid ,about 80%