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: Pathology
[{'content': 'The most reliable investigation in amyloid disease is - \nSelect and explain. \nA. Rectal biopsy, B. Immunoglobulin assay, C. Ultrasound, D. Urine examination', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Rectal biopsy", 'role': 'assistant'}]