This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pathology
[{'content': 'Which of the following is the least common site of atherosclerotic lesions \nSelect and explain. \nA. Aoic bifurcation, B. Pulmonary aerial trunk, C. Common carotid aery, D. Middle cerebral aery', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Atherosclerosis is an intima-based lesion composed of a fibrous cap and an atheromatous (literally, "gruel-like") core; the constituents of the plaque include smooth muscle cells, ECMs, inflammatory cells, lipids, and necrotic debris. The impoance of hemodynamic factors in atherogenesis is illustrated by the observation that plaques tend to occur at ostia of exiting vessels, at branch points, and along the posterior wall of the abdominal aoa, where there is turbulent blood flow. In vitro studies fuher demonstrate that nonturbulent laminar flow leads to the induction of endothelial genes whose products protect against atherosclerosis. (Robbins Basic Pathology,9th edition,pg no.338)', 'role': 'assistant'}]