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: Pathology
The defect in Berry aneurysm lies in: 
Select and explain. 
A. Degeneration of internal elastic lamina, B. Degeneration of media / muscle cell layer of aery, C. Deposition of mucoid material in media, D. Low grade inflammation of vessel wall
B: Degeneration of media / muscle cell layer of aery
Answer: B: Degeneration of media / muscle cell layer of aery 
Explanation: . Degeneration of media / muscle cell layer of aery