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': 'Eruption of upper canine ahead of upper premolars ; most probable reason being \nSelect and explain. \nA. Upper premolars are crowded, B. Upper premolars are impacted, C. Only upper first premolar is impacted, D. Only upper 2nd molar is impacted', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]