This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
[{'content': 'Trolly tract sign is seen in - \nSelect and explain. \nA. Achondroplasia, B. Psoriatic ahritis, C. Osteopetrosis, D. Ankylosing spondylitis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Trolly track sign : The Central radiodense line on frontal radiographs is related to ossification of supraspinous and interspinous ligaments. In addition, there are two more lateral veical linear lines, which represent ossification of the apophyseal joint capsules. The three veical ossified lines together make up the trolley-track sign. Radiological features of Ankylosis spondylitis are : Sacroiliitis Enthesopathy Romanus lesions Bamboo spine Rugger Jersy spine Interveebral disc calcification Dagger sign Trolley track sign Squarring of veebrae.', 'role': 'assistant'}]