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: Radiology
[{'content': 'Penny test is the quality assurance test to detect \nSelect and explain. \nA. Fixer depletion, B. Unsafe illumination, C. Machine malfunction, D. Contaminated solution', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]