<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 65-year-old veteran with a history of hypertension, diabetes, and end-stage renal disease presents with nausea, vomiting, and abdominal pain. The patient was found to have a small bowel obstruction on CT imaging. He is managed conservatively with a nasogastric tube placed for decompression. After several days in the hospital, the patients symptoms are gradually improving. Today, he complains of left leg swelling. On physical exam, the patient has a swollen left lower extremity with calf tenderness on forced dorsiflexion of the ankle. An ultrasound confirms a deep vein thrombus. An unfractionated heparin drip is started. What should be monitored to adjust heparin dosing?? A: Prothrombin time, B: Activated partial thromboplastin time, C: Internationalized Normal Ratio INR, D: Creatinine level, E: Liver transaminase levels,  <response>: This is a clinical vignette about a 65-year-old man with multiple medical comorbidities who developed a small bowel obstruction that was managed conservatively. He later developed a deep vein thrombosis in his left leg and was started on an unfractionated heparin drip. The question asks what laboratory value should be monitored to adjust the heparin dosing.Choice A, prothrombin time, measures the extrinsic coagulation pathway and is used to monitor warfarin therapy, not heparin. Choice B, activated partial thromboplastin time aPTT, measures the intrinsic coagulation pathway and is used to monitor unfractionated heparin therapy. This is the correct answer.Choice C, INR, is used to monitor warfarin therapy, not heparin. Choice D, creatinine, may be monitored in a patient with renal insufficiency to avoid heparin accumulation, but is not used to titrate heparin dosing.Choice E, liver enzymes, may be monitored to detect heparin-induced thrombocytopenia, but are not used to titrate heparin dosing.In summary, aPTT is used to monitor and adjust dosing of intravenous unfractionated heparin.B: Activated partial thromboplastin time 