<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 52-year-old man presents to the emergency department because of pain and swelling in his left leg over the past few hours. He traveled from Sydney to Los Angeles 2 days ago. He has had type 2 diabetes mellitus for 10 years and takes metformin for it. He has smoked a pack of cigarettes daily for 25 years. His temperature is 36.9C 98.4F, the blood pressure is 14090 mm Hg, and the pulse is 90min. On examination, the left calf is 5 cm greater in circumference than the right. The left leg appears more erythematous than the right with dilated superficial veins. Venous duplex ultrasound shows non-compressibility. Which of the following best represents the mechanism of this patients illness?? A: Impaired arterial blood flow, B: Impaired venous blood flow, C: Impaired lymphatic blood flow, D: Subcutaneous soft-tissue infection that may extend to the deep fascia, E: Infection of the dermis and subcutaneous tissues,  <response>: This is a clinical vignette describing a patient with unilateral leg swelling and erythema after a long flight. The key findings are calf swelling, dilated superficial veins, and noncompressible veins on ultrasound, which indicate impaired venous blood flow. The differential diagnosis includes deep vein thrombosis DVT, which can occur after prolonged immobility during travel. The patient has several risk factors for DVT including older age, diabetes, smoking, and recent travel. The mechanism is likely impaired venous blood flow due to DVT formation.B: Impaired venous blood flow 