This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anemia and RBC Disorders, Subject name: Medicine
HbH is characterized by: 
Select and explain. 
A. Deletion of three alpha chain genes, B. Deletion of three alpha chains and one beta chain genes, C. Deletion of two alpha and two beta chain genes, D. Deletion of four alpha chain genes
A: Deletion of three alpha chain genes
Answer: A: Deletion of three alpha chain genes 
Explanation: Ans. A. Deletion of three alpha chain genesAlpha-ThalassemiaSilent carrier state1 gene deletion-aaaa thalassemia trait2 gene deletion-a-aHbH disease3 gene deletion---aHydrops fetalis4 gene deletion----