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': 'Which of the following causes flexion of the lumbar spine? \nSelect and explain. \nA. Erector spinae, B. External obliques muscle, C. Internal oblique muscle, D. Psoas major', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Flexion of lumbar spine is caused by bilateral action of the rectus abdominis and psoas major. Gravity may also play a role. Bilateral action of the erector spinae, multifidus and semispinalis thoracis cause extension of the lumbar spine. Unilateral action of the external oblique, internal oblique, longissimus thoracis, multifidus, quadratus lumborum, rhomboids, serratus anterior, iliocostalis and lumborum results in lateral bending.Also know:Unilateral action of rotators, multifidus, iliocostalis, longissimus, external oblique acting synchronously with opposite internal oblique and splenius cervicis.', 'role': 'assistant'}]