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: Social & Preventive Medicine
[{'content': "Ten readings of BP taken before and after treatment is studied by - \nSelect and explain. \nA. Paired 't' test, B. 'Z' test, C. Students `t' test, D. Correlation test", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]