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: Anatomy
[{'content': 'Flexor of lumbar spine is/are -a) Erector spineb) External oblique musclec) Internal oblique muscled) Rectus abdominise) Psoas major \nSelect and explain. \nA. ad, B. be, C. ace, D. de', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Rectus abdominis, psoas major and gravity are principal flexors of thoracolumbar vertebrae.', 'role': 'assistant'}]