This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
[{'content': 'Blood brain barrier is formed by? \nSelect and explain. \nA. Foot processes of astrocytes and endothelial cells, B. Foot processes of oligodendrocytes and endothelial cells, C. Foot process of microglia and endothelia cells, D. Foot process of glial cells and endothelial cells', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Foot processes of astrocytes and endothelial cells', 'role': 'assistant'}]