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: Medicine
[{'content': 'Best investigation when there is clinical suspicio of pulmonary embolism in a patient is - \nSelect and explain. \nA. D - Dimer assay, B. Multi detector CT angiography, C. Doppler ultrasound, D. Catheter angiography', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]