Answer:
B. the endothelium of CNS capillaries forms a blood-brain barrier
Explanation:
Commonly known as the blood-brain barrier or BBB is formed by the action of endothelial cells of brain which line the cerebral microvasculature. The BBB is a vital mechanism that protects the brain from the action of many circulating agents which are present in different medications like xenobiotics or other neurotransmitters which can disrupt the neural functions or harm them. The BBB also functions to protect the brain from the fluctuations in plasma composition of brain cells.
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