This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Which of the following do not contribute to hilar shadow \nSelect and explain. \nA. Pulmonary arteries, B. Upper lobe pulmonary veins, C. Lower lobe pulmonary veins, D. Lobar bronchi', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Lower lobe veins do not cross the hila and therefore do not contribute to hilar shadow.', 'role': 'assistant'}]