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: Dental
[{'content': 'Placing a ring liner approximately 3.25 mm short of the ends of the ring tends to \nSelect and explain. \nA. Produce a more uniform expansion and the expansion will not be in a vertical direction hence no distortion, B. Produce a more uniform contraction, C. Produce no change, D. Produce distortion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]