<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 33-year-old man presents to a physician with a 3-year history of gradually worsening tics and difficulty walking. He was last seen by the physician 5 years ago for anxiety and has been purchasing anti-anxiety medications from an internet website without a prescription because he cannot afford to pay for the office visits. Now he says his anxiety is somewhat controlled, but the motor difficulties are making it difficult for him to work and socialize. His family history is unknown because his parents died in an automobile accident when he was an infant. He grew up in foster care and was always a bright child. An MRI of the brain is ordered, which shows prominent atrophy of the caudate nucleus. Repeats of which of the following trinucleotides are most likely responsible for this patients disorder?? A: CCG, B: CGG, C: GAA, D: CAG, E: CTG,  <response>: This is a clinical vignette describing a 33-year-old man with a 3-year history of worsening tics and difficulty walking. He also has a history of anxiety. The MRI shows atrophy of the caudate nucleus. Based on the clinical presentation of tics, movement issues, and caudate atrophy, this patient likely has Huntingtons disease. Huntingtons disease is caused by expanded CAG trinucleotide repeats in the huntingtin gene on chromosome 4. Therefore, the answer is D, as CAG repeats are most likely responsible for this patients disorder.D: CAG 