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: Medicine
[{'content': 'Which of the following is caused by deletion of all four alpha globin genes \nSelect and explain. \nA. Beta thalassemia major, B. Hb Bas, C. HbH, D. adeg thalassemia trait', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Hb Bas", 'role': 'assistant'}]