This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'A substance is present in a concentration of 2mg% in the afferent arteriole and zero mg% in the efferent. True about the substance is \nSelect and explain. \nA. It is free filtered in glomerulus, B. Secreted in cortical nephron, C. Absorbed in PCT, D. Impermeable in loop of Henle', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Afferent arteriole was having the substance. After it passed through the glomerulus, in the efferent arteriole it is absent. That means all of it was filtered out through the glomerulus.', 'role': 'assistant'}]