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': 'With indirect spruing, which one of the following porosities can be minimised \nSelect and explain. \nA. Back pressure porosity, B. localized shrinkage porosity, C. Pin hole porosity, D. Micro porosity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]