<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 20-month-old boy is brought to the emergency department by his parents with fever and diarrhea that have persisted for the past 2 days. He has a history of repeated bouts of diarrhea, upper respiratory tract infections, and failure to thrive. His vital signs are as follows: blood pressure 8040 mm Hg, pulse 130min, temperature 39.0C 102.2F, and respiratory rate 30min. Blood tests are suggestive of lymphopenia. The child is diagnosed with severe combined immune deficiency after additional testing. Which of the following is the most common association with this type of immunodeficiency?? A: X-linked severe combined immunodeficiency, B: Adenosine deaminase deficiency, C: Janus-associated kinase 3 JAK3 deficiency, D: Reticular dysgenesis, E: Bare lymphocyte syndrome,  <response>: This is a clinical vignette describing a 20-month-old boy with fever, diarrhea, failure to thrive, and recurrent infections, who is diagnosed with severe combined immunodeficiency SCID after testing shows lymphopenia. The question asks about the most common association with this type of immunodeficiency. Based on the clinical presentation and lymphopenia, this is likely X-linked SCID. X-linked SCID is the most common type of SCID and is caused by a mutation in the IL2RG gene on the X chromosome. It presents in infancy with recurrent severe infections, failure to thrive, and lymphopenia.The other answer choices describe less common genetic causes of SCID:- Adenosine deaminase ADA deficiency - Janus kinase 3 JAK3 deficiency- Reticular dysgenesis- Bare lymphocyte syndromeTherefore, the correct answer is likely X-linked severe combined immunodeficiency.A: X-linked severe combined immunodeficiency 