<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 12-year-old boy presents to the emergency department with a swollen and painful knee. He says that he was exploring with his friends when he tripped and hit his knee against the ground. He didnt feel like he hit it very hard but it started swelling and becoming very painful. His mom reports that he has always been prone to bleeding from very minor trauma and that others in the family have had similar problems. Based on clinical suspicion a coagulation panel was obtained showing a prothrombin time PT of 10 seconds normal range 9-11 seconds, a partial thromboplastin time PTT of 45 seconds normal 20-35 seconds, and a normal ristocetin cofactor assay equivalent to bleeding time. Mixing tests with factor IX and XI do not show complementation, but mixing with factor VIII reverses the coagulation abnormality. Which of the following is the most likely diagnosis for this patient?? A: Bernard-Soulier disease, B: Glanzmann thrombasthenia, C: Hemophilia A, D: Hemophilia B, E: von Willebrand disease,  <response>: Based on the information provided in the question stem, the key findings are:- 12-year-old boy with swollen and painful knee after minor trauma- History of easy bruisingbleeding with minor trauma- Prolonged PTT on coagulation testing- Mixing tests show correction of coagulopathy with addition of factor VIII, but not factors IX or XI- Normal PT, ristocetin assayThis presentation is most consistent with hemophilia A. The easy bruisingbleeding with minor trauma points towards a bleeding disorder. The isolated prolongation of PTT narrows the differential, as PT is normal. Mixing studies confirm a deficiency of factor VIII. The other disorders can be ruled out based on the mixing study results and normal ristocetin assay.C: Hemophilia A 