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
Flexor of lumbar spine is/are: 
Select and explain. 
A. Erector spinae, B. External oblique muscle, C. Internal oblique muscle, D. Rectus abdominis
D: Rectus abdominis
Answer: D: Rectus abdominis 
Explanation: D i.e. Rectus abdominisRectus abdominis, psoas major & gravity are principal flexors of thoracolumbar veebraeQ. Mn-"Bilateral Major GRAP"