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: Biochemistry
[{'content': 'The first gene therapy (somatic enzyme) was successfully done in - \nSelect and explain. \nA. SCID, B. Phenylketonuria, C. Thalassemia, D. Cystic fibrosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: SCID was 1st disease that was successfully treated by gene therapy.', 'role': 'assistant'}]