This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc. (R.B.C), Subject name: Pathology
[{'content': 'Hemoglobin H disease is caused by deletion \nSelect and explain. \nA. Single a globin chain, B. Two a globin chains, C. Three a globin chains, D. All a globin chain', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) Three a globin chains(Ref: Robbins 9th/pg 638)Classification of a-thalassemia:Normally 4 a-genes synthesize: 2 a chains -> a, a / a, aMost common cause of a -thalassemia is a -gene deletion (frame-shift mutation)9', 'role': 'assistant'}]