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': 'Localised shrinkage porosity is seen when there is \nSelect and explain. \nA. Thin sprue, B. Investment heated strongly, C. Inadequate air discharge, D. Low casting pressure', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]