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: Pathology
[{'content': 'Which of the following cells do Natural killer cells attack? \nSelect and explain. \nA. Cells which express MHC 1, B. Cells which are not able to express MHC 1, C. MHC cells which express MHC 2, D. Cells which are not able to express MHC', 'role': 'user'}, {'content': 'Answer: B \nExplanation: . Cells which are not able to express MHC 1', 'role': 'assistant'}]