This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Circulation, Subject name: Physiology
The blood-brain barrier is thought to exist because capillaries in the central nervous system have which of the following characteristics? 
Select and explain. 
A. Discontinuous basal lamina, B. Fenestrae with diaphragms, C. Fenestrae without diaphragms, D. A few pinocytic vesicles
D: A few pinocytic vesicles
Answer: D: A few pinocytic vesicles 
Explanation: Capillaries in the CNS have a continuous basal lamina and thus lack fenestrae. In contrast to continuous capillaries in other pas of the body, they contain only a few pinocytic vesicles; this characteristic is thought to be paly responsible for the blood-brain barrier