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: \nSelect and explain. \nA. Erector spinae, B. External oblique muscle, C. Internal oblique muscle, D. Rectus abdominis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Rectus abdominisRectus abdominis, psoas major & gravity are principal flexors of thoracolumbar veebraeQ. Mn-"Bilateral Major GRAP"', 'role': 'assistant'}]