This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Crystal Ahropathy, Subject name: Medicine
[{'content': 'In a patient with gouty ahritis,synol fluid aspiration was done,strongly negative birefringent needle shaped crystals were seen under polarized light .These crystals are composed of which of the following ? \nSelect and explain. \nA. Monosodium urate, B. Calcium pyrophosphate, C. Sodium pyrophosphate, D. Homogentisic acid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Crystals of monosodium urate are needle-shaped, 5-25 mm in length, and strongly negatively bifringent under polarized light. Crystallization of monosodium urate in synol fluid and tissues results in a dramatic inflammatory response characterized by erythema, edema, and intense pain. Double contour cailage line on USG is seen', 'role': 'assistant'}]