This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Back region, Subject name: Anatomy
[{'content': 'A 25-year-old soldier suffers a gunshot wound on the lower pa of his back and is unable to move his legs. A neurologic examination and magnetic resonance imaging (MRI) scan reveal injury of the cauda equina. Which of the following is most likely damaged. \nSelect and explain. \nA. Dorsal primary rami, B. Ventral primary rami, C. Dorsal roots of the thoracic spinal nerves, D. Ventral roots of the sacral spinal nerves', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The cauda equina is the collection of dorsal and ventral roots of the lower lumbar and sacral spinal nerves below the spinal cord. Dorsal and ventral primary rami and dorsal roots of the thoracic spinal nerves and lumbar spinal nerves do not paicipate in the formation of the cauda equina', 'role': 'assistant'}]