This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pulmonary Thromboembolism and Deep-Vein Thrombosis, Subject name: Medicine
A patient develops pulmonary thromboembolism due to? 
Select and explain. 
A. DIC, B. Coagulation disorder, C. DVT, D. Venous hyper tension
C: DVT
Answer: C: DVT 
Explanation: ANSWER: (C) DVTREF: Harrison 17th ed chapter 265When venous thrombi dislodge from their site of formation, they embolize to the pulmonary arterial circulation or, paradoxically, to the arterial circulation through a patent foramen ovale or atrial septal defect. About half of patients with pelvic vein thrombosis or proximal leg DVT develop PE, which is usually asymptomatic. Isolated calf vein thrombi pose a much lower risk of PE, but they are the most common source of paradoxical embolism.