This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Aerial disorders, Subject name: Surgery
All of the following are true about aoic aneurysm except:- 
Select and explain. 
A. Saccular aneurysm involves whole circumference, B. True aneurysm involves all 3 layers, C. Atherosclerosis is the commonest cause, D. False aneurysm is not covered by all 3 layers
A: Saccular aneurysm involves whole circumference
Answer: A: Saccular aneurysm involves whole circumference 
Explanation: Degenerative aneurysms ( caused by atherosclerosis) are MC AAA (90%) . True (all three layers of vessel are involved), false (do not have all three layers of vessel) Infected (mycotic) aneurysm are false aneurysm Dissecting aneurysm (dissection with aneurysmal dilatation of false lumen) Fusiform (symmetrical enlargement involving whole circumference of aery) Saccular (affect only pa of the aerial circumference) have higher risk of rupture