This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Psychiatry
[{'content': 'Best marker for electroconvulsive therapy: \nSelect and explain. \nA. CSF 5 HIAA, B. CSF serotonin, C. Brain derived growth factor, D. CSF dopamine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Increase in brain derived neurotrophic factor, BDNF mediates the response to ECT and is the best marker for the same.', 'role': 'assistant'}]