<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 67-year-old woman who was recently diagnosed with Crohn disease comes to the physician for evaluation of her immunosuppressive therapy. She has had recurrent flares since her diagnosis. Physical examination shows two shallow ulcers on her oral mucosa. The physician considers adding azathioprine to her medication regimen. A deficiency of which of the following enzymes would diminish the therapeutic effect of this drug?? A: Xanthine oxidase, B: Thymidylate synthase, C: Phosphoribosyl pyrophosphate synthetase, D: Hypoxanthine-guanine phosphoribosyl transferase, E: Dihydrofolate reductase,  <response>: This is a medical question asking about which enzyme deficiency would diminish the therapeutic effect of azathioprine in a patient with Crohns disease. Azathioprine is an immunosuppressive drug that works by inhibiting purine synthesis. The key is to identify which enzyme is involved in purine synthesis and metabolism that would affect azathioprine mechanism of action if deficient.D: Hypoxanthine-guanine phosphoribosyl transferase 