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': 'The main purpose of etching enamel before placement of composite is: \nSelect and explain. \nA. To increase the surface area and surface energy, B. To provide micro mechanical interlocking, C. To provide proper adaptation and decrease microleakage, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]